you just need to get your OBC certificate corrected and need to inform the CAT helpdesk about this error.
Great Lakes - PGDM & PGPM Admissions 2026
Admissions Open | Globally Recognized by AACSB (US) & AMBA (UK) | 17.8 LPA Avg. CTC for PGPM 2025
CAT Admit Card Date:05 Nov' 25 - 30 Nov' 25
Dear CAT aspirants, if you are planning to prepare for the Number System, this article is created especially for you. Here, you will find the key properties of numbers that cover a major part of the syllabus and help you solve around 70% of the questions from this topic in the CAT Quantitative Aptitude section. In CAT 2025, you can expect 3-4 questions from Number System, and mastering these properties will give you a clear advantage. In this article, careers360 will provide you 5 most important properties of numbers for CAT that covers 70% of CAT number system questions.
This Story also Contains
Do you know
Importance of numbers in CAT QA?
What are the CAT number system shortcuts?
What are the CAT number system preparation strategies?
how to solve number system questions in CAT?
This article is going to help you to get your answers……
The CAT Number System topics from which most of the questions are asked in exams are:
Properties of numbers
Factorization
Divisibility rule
HCF and LCM
Unit digit
Last two digits
Base system
In CAT, Divisibility rules are used
To determine whether a given number is divisible by another number leaving no Remainder.
To find the missing digit in a given number.
Admissions Open | Globally Recognized by AACSB (US) & AMBA (UK) | 17.8 LPA Avg. CTC for PGPM 2025
Ranked No. 3 Business School in India and no.35 in world by Financial Times MiM 2025 Ranking | Highest CTC: INR 89 LPA
Divisor |
Divisibility condition |
Examples |
2 |
The last digit is even (0, 2, 4, 6, or 8). |
All Even numbers |
3 |
Sum the digits. If the result is divisible by 3, then the original number is divisible by 3. |
4359 → 4 + 3 + 5 + 9 = 21 which is divisible by 3. |
4 |
Examine the last two digits. |
40864: 64 is divisible by 4. So, 40864 is divisible by 4. |
5 |
The last digit is 0 or 5. |
685: the last digit is 5. 4590: last digit is 0. Both numbers are divisible by 5. |
6 |
It is divisible by 2 and by 3. |
1,458: 1 + 4 + 5 + 8 = 18, so it is divisible by 3 and the last digit is even, hence the number is divisible by 6. |
7 |
A number is divisible by 7 if the difference between twice the unit digit and the number formed by the remaining digits is divisible by 7. |
343: 34-2×3=28 which is divisible by 7. Hence, 343 is divisible by 7. |
8 |
A number is divisible by 8 if the number formed by its last three digits is divisible by 8. |
34152: Examine divisibility of just 152: 19 × 8 So, the number is divisible by 8. |
9 |
Sum the digits. If the result is divisible by 9, then the original number is divisible by 9. |
435429 → 4 + 3 + 5 + 4 + 2 + 9 = 27 which is divisible by 9. |
11 |
A number is divisible by 11 if the difference between the sum of digits at odd places (1st, 3rd, 5th, etc.) and the sum of digits at even places (2nd, 4th, 6th, etc.) is either 0 or divisible by 11. |
918,082: 9 − 1 + 8 − 0 + 8 − 2 = 22. So, the number is divisible by 11. |
Divisibility rules can be applied in finding the factors of a given number directly.
For example:
If a number has either 0 or 5 at unit place, it must have a factor 5.
If a number has an even digit at unit place, it must have a factor 2.
If the sum of the digits of the number is divisible by 3, it must have a factor 3.
Similarly, we can apply the divisibility rules of 6, 9, 11 etc.
If you need to find the prime factorization, use the divisibility rule of prime numbers.
In CAT, concept of factors and multiples are used to
Determine the number of factors
HCF and LCM
Factor: A factor of a number divides evenly into that number, leaving no remainder.
Example: Factors of 48 = 1, 2, 3, 4, 6, 8, 12, 16, 24
Multiple: A multiple of a number is the result of multiplying that number by another whole number.
Example: Multiples of 48 = 48, 96, 144, ……
1. Number of factors:
Concept/ Formula: For $N=a^p×b^q ×c^r×….$ Where a, b, and c are prime factors. p, q, r are positive integers.
Number of all factors = $(p+1)(q+1)(r+1)….$
$N =1280=2×2×2×2×2×2×2×2×5=2^8×5$
Number of factors = (8 + 1) × (1 + 1) = 18
2. Sum of all factors:
Concept/ Formula: For $N=a^p×b^q ×c^r×….$ Where a, b, and c are prime factors. p, q, r are positive integers.
Sum = $(1+a^1+a^2+⋯+a^p )(1+b^1+b^2+⋯+b^q )(1+c^1+c^2+⋯.+c^r )…..$
$N =1280=2×2×2×2×2×2×2×2×5=2^8×5$
Sum of all factors = $(1+2+2^2+⋯+2^8 )(1+5) =(2^9-1)/(2-1)×6=511×6=3066$
Highest Common Factor (HCF):
The HCF of two or more numbers is the largest positive integer that divides them without leaving a remainder. It is also known as the Greatest Common Divisor (GCD). HCF is used to solve problems related to dividing objects into smaller equal groups.
Least Common Multiple (LCM):
The LCM of two or more numbers is the smallest multiple that is evenly divisible by all of the given numbers. LCM is useful when solving problems that involve finding the least number of repetitions required for multiple events to synchronise or repeat together.
HCF and LCM of fractions:
HCF (Highest Common Factor) of fractions
The HCF of two or more fractions is the largest fraction that can exactly divide each given fraction. To find the HCF of fractions, we need to find the HCF of the numerators and the LCM of the denominators. We’ll find HCF and LCM of the numbers using:
LCM (Least Common Multiple) of fractions
The LCM of two or more fractions is the smallest fraction that is divisible by each of the given fractions. To find the LCM of fractions, we need to find the LCM of the numerators and the HCF of the denominators.
The concept of even and odd digits in CAT is useful to verify answers of number system questions.
The concept of prime and composite is useful for prime factorization, HCF and LCM questions.
Classification of numbers into Even and Odd Numbers:
Non – negative integers are classified into even and odd numbers.
Odd Numbers: A whole number that is not exactly divisible by 2 is called an odd number.
For example: 3, 5, 7, 9, 11, 13, 15, are odd number.
Or a number having 1, 3, 5, 7, and 9 at its unit’s place is called an odd number.
Even Numbers: A whole number exactly divisible by 2 is called an even number.
For example: 0, 2, 4, 6, 8, 10, 12, 14, 16 .......................... are even number.
Or a number having 0, 2, 4, 6, 8 at its unit’s place is called an even number.
Important Results on Even and Odd Integers:
Classification of numbers into Prime and Composite Numbers:
Natural Numbers can be classified as
Prime Number: Prime numbers are those numbers which is greater than I, and have only two factors-1 and the number itself. Prime numbers are divisible only by the number 1 or itself.
Example: 2, 3, 5, 7, and 11 are the first few prime numbers.
Composite Number: Numbers having more than two factors are called composite numbers.
Example: 4, 6, 9, 10, and 15 are a few examples of composite numbers.
Note:
1. Co-Prime Numbers:
A pair of numbers that have exactly one factor in common.
Example:
16 and 25
Factors of 16: 1, 2, 4, 8, 16
Factors of 25: 1, 5, 25
Common factor: 1
2. All prime numbers are co-prime with each other.
3. 2 is the smallest prime number.
4. 2 is the only even prime number.
5. For quick answer, you should remember
The concept of remainders in CAT is used
To determine the remainder of a large number divided by another number.
To find the unit digit and last digit of a number
Basic Remainder Theorem to find the remainder when a large number is divided by small numbers:
It is better to understand this with the help of examples:
Question: Find the remainder when $6789^{12345}$ is divided by 8.
Solution:
Divide $6789^{12345}$ by 8, remainder will be of the form $5^{12345}$ ≡ $5×5^{12344}≡5×25^{6172}$
Now, divide it by 8, remainder will be 5.
Binomial theorem to find the remainder:
The Binomial Theorem states that for any positive integer n and any real numbers a and b:
[a+bn=k=0n knCan-kbk]
Example: Find the remainder when $27^{10}$ is divided by 5.
Solution:
$27^{10}= (25+2)^{10}$, if we divide this number by 5, the remainder will be $2^{10}$.
Now divide $2^{10}$ by 5 to find the final remainder.
So, when$2^{10}$ divided by 5, remainder = 4
Concept of Cyclicity to find unit digit:
Unit digit cyclicity refers to the repetition pattern of the unit digit (the digit in the one’s place) of a number. To determine the unit digit cyclicity of a number, we need to analyse the cyclicity of its unit digit (also known as the ones digit) raised to various powers.
Formula for Unit Digit Cyclicity:
The unit digit of any number raised to a power follows a specific cyclicity pattern.
To find the unit digit of an where a is the unit digit and n is any natural number.
Digit |
Cyclicity |
Unit digit |
Remark |
1 |
1 |
1 |
|
2 |
4 |
The unit digit repeats every four powers (2,4,8,6). |
|
3 |
4 |
The unit digit repeats every four powers (3,9,7,1) |
|
4 |
2 |
4,6 |
4 raised to power any even number gives 6 otherwise 4. |
5 |
1 |
5 |
|
6 |
1 |
6 |
|
7 |
4 |
The unit digit repeats every four powers (7,9,3,1) |
|
8 |
4 |
The unit digit repeats every four powers (8,4,2,6) |
|
9 |
2 |
9,1 |
9 raised to power any even number gives 1 otherwise 9. |
0 |
1 |
0 |
|
Example 1: $2^1=2,2^2=4,2^3=8,2^4=16,2^5=32,2^6=64$ and so on. The unit digit repeats every four powers (2,4,8,6).
Example 2: $4^1=4,4^2=16,4^3=64,4^4=256$, and so on. The unit digit alternates between 4 and 6.
Rules to determine the last two digits of the number:
Rule 1: For the numbers of the form $x^2 /(50±x)^2 / (100±x)^2…, x^2$ will be the last two digits.
Example: Find the last two digits of $96^2$.
Solution: $96^2 = (100-4)^2$
Last two digits = $4^2=16$
Rule 2: For the numbers having last digit odd except 5.
For (odd)20k, last two digits = 01, k is positive integer.
Example: Find the last two digits of 2342.
Solution: $23^42=23^40×23^2$
Last two digits = 01 × 29 = 29, [Here 29 are the last two digits of 232]
Rule 3: For the numbers having last digit 5.
For (odd5)^odd, last two digits = 75, otherwise 25.
Example: Find the last two digits of 2542 and 7575.
Solution: 2542, last two digits 25, since the digit before 5 is even in 25.
7575, last two digits 75, since the digit before 5 is odd in 75 and the power is odd.
Rule 4: For the numbers having last digit even.
For (Even)^20k, last two digits = 76, k is positive integer.
Example: Find the last two digits of 4624.
Solution:
$46^24=46^20×46^2×46^2$
Writing the last two digits of each term
Last two digits ≡ 76 × 16 × 16
Last two digits ≡ 76 × 56
Last two digits ≡ 56
Sum of the digits of a number till single digit.
Example: To find digit sum of 28976
Step 1: 2 + 8 + 9 + 7 + 6 = 32
Step 2: 3 + 2 = 5 (Ans)
Rule 1: If the digit-sum of a number is 9, then we can eliminate the 9 straight away and the digit- sum becomes ‘zero.’
Rule 2: While solving problems if the digit sum value comes negative then just add it to 9 & result will be the actual digit sum value.
Application in Divisibility by 3 and 9:
A number is divisible by 3 if the sum of its digits is divisible by 3.
Example: Check whether 3987654 is divisible by 3.
Sum of the digits = 3 + 9 + 8 + 7 + 6 + 5 + 4 = 42
42 = 4 + 2 = 6 which is divisible by 3. So, the given number is divisible by 3.
A number is divisible by 9 if the sum of its digits is divisible by 9.
Example: Check whether 3987657 is divisible by 9.
Sum of the digits = 3 + 9 + 8 + 7 + 6 + 5 + 7 = 45
45 = 4 + 5 = 9 which is divisible by 9. So, the given number is divisible by 9.
Application in Missing Digit Problems:
This technique extends to solving for a missing digit by substituting it into the digit sum equation.
Example: In the number 2345x2 is divisible by 3, find possible values of x.
Digit sum = 2 + 3 + 4 + 5 + x + 2 = 16 + x
So, possible values of x are 2, 5, 8 so that sum of digits is divisible by 3 and hence number will be divisible by 3 for x = 2, 5, 8
Example: For the number 6523678pq, find the smallest possible sum of p and q so that the number is divisible by 9.
The sum of the known digits is 6 + 5 + 2 + 3 + 6 + 7 + 8 + p + q = 37 + p + q. For this number to be divisible by 9, the sum of all digits must be a multiple of 9. So, 37 + p + q must be a multiple of 9. The smallest multiple of 9 greater than 37 is 45, so p + q = 45 - 37 = 8.
These properties work because most of the CAT numbers questions reduce to these 5 concepts.
Concept |
Question Type |
Divisibility & Factors |
Prime factorization HCF & LCM Finding number of factors / sum of factors Divisibility rules through digit sums (9, 11 tests etc.) |
Remainders & Modular Arithmetic |
Finding last digit / cyclicity Remainder theorems Divisibility-based remainder patterns |
Base System & Units/Last Digits |
Conversion between bases Identifying units digit / last two digits Place value logic |
Even–Odd, Positives–Negatives & Digit Properties |
Sum/product of digits properties Solution check through even and odd digit properties
|
Factors and Multiples |
Trailing zeros Number of factors Sum of factors |
CAT number system questions with solutions
Q.1) A school has less than 5000 students and if the students are divided equally into teams of either 9 or 10 or 12 or 25 each, exactly 4 are always left out. However, if they are divided into teams of 11 each, no one is left out. The maximum number of teams of 12 each that can be formed out of the students in the school is:
A) 150
B) 140
C) 145
D) 135
Solution:-
Since the total number of students, when divided by either 9 or 10 or 12 or 25 each, gives a remainder of 4, the number will be in the form of LCM(9,10,12,25)k + 4 = 900k + 4.
It is given that the value of (900k + 4) is less than 5000.
Also, it is given that (900k + 4) is divided by 11.
It is only possible when k = 2 and total students = 1804.
So, the number of 12 students group = $\frac{1800}{12}$ = 150
Hence, the correct answer is option (1).
Q.2) When $10^{100}$ is divided by 7, the remainder is
A) 3
B) 4
C) 6
D) 7
Solution:-
We know that $10 \div 7$ leaves a remainder of $3$, so $10^{100}$ will leave the same remainder as $3^{100}$ when divided by $7$
Now, $3^3 = 27$ and $27 \div 7$ leaves remainder $-1$ (since $27 = 28 - 1$)
So, $3^{100} = (3^3)^{33} \times 3 = 27^{33} \times 3$
This becomes $(-1)^{33} \times 3 = -3$
So, the remainder is $-3$.
Since we want a positive remainder, add $7$: $-3 + 7 = 4$
The remainder is 4.
Hence, the correct answer is option 2.
Q.3) For some natural number n, assume that (15,000)! is divisible by n!. The largest possible value of n is
A) 4
B) 7
C) 6
D) 8
Solution:-
To find the largest possible value of n, we need to find the value of n such that n! is less than 15000.
$7!=5040$
$8!=40320 > 15000$
This implies 15000! is not divisible by 40320.
Therefore, the maximum value n can take is 7.
Hence, the correct answer is 7.
Q.4) Minu purchased a pair of sunglasses for Rs.1000 and sold them to Kanu for 20% profit. Then, Kanu sells it back to Minu at a 20% loss. Finally, Minu sells the same pair of sunglasses to Tanu. If the total profit made by Minu from all her transactions is Rs.500, then the percentage of profit made by Minu when she sold the pair of sunglasses to Tanu is
A) 35.42%
B) 31.25%
C) 52%
D) 54%
Solution:-
Initial Cost Price for Minu = 1000
Cost Price to Kanu = 120% of 1000 = 1200
Profit made by Minu = 1200 – 1000 = 200
Again Minu purchased at 80% of 1200 = 960
The total profit made by Manu is 500. So, profit made when she sold it to Tanu = 500 – 200 = 300
Final Selling Price for Minu when sold to Tanu = 960 + 300 = 1260
Profit percent = $\frac{300}{960}$ $\times$ 100 = 31.25%
Hence, the correct answer is option (2).
Q.5) Ankita buys 4 kg cashews, 14 kg peanuts and 6 kg almonds when the cost of 7 kg cashews is the same as that of 30 kg peanuts or 9 kg almonds. She mixes all the three nuts and marks a price for the mixture in order to make a profit of Rs.1752. She sells 4 kg of the mixture at this marked price and the remaining at a 20% discount on the marked price, thus making a total profit of Rs. 744. Then the amount, in rupees, that she had spent in buying almonds is:
A) 1680
B) 1176
C) 2520
D) 2530
Solution:-
It is given,7C = 30P = 9A and Ankita bought 4C, 14P and 6A.
Let 7C = 30P = 9A = 630k
C = 90k, P = 21k, and A = 70k
Cost price of 4C, 14P and 6A = 4(90k)+14(21k)+6(70k) = 1074k
Marked up price = 1074k + 1752
$\begin{aligned} & \text { S.P }=\frac{1}{6}(1074 k+1752)+\left(\frac{4}{5}\right)\left(\frac{5}{6}\right)(1074 k+1752)=\frac{5}{6}(1074 k+1752) \\ & \text { S.P-C.P }=\text { profit } \\ & 1460-\frac{1074 k}{6}=744 \\ & \frac{1074 k}{6}=716\end{aligned}$
k = 4
Money spent on buying almonds = 420k = 420 × 4 = Rs 1680
The correct answer is Rs. 1680.
Q.6) Amal buys 110 kg of syrup and 120 kg of juice, syrup being 20% less costly than juice, per kg. He sells 10 kg of syrup at 10% profit and 20 kg of juice at 20% profit. Mixing the remaining juice and syrup, Amal sells the mixture at Rs 308.32 per kg and makes an overall profit of 64%. Then, Amal’s cost price for syrup, in rupees per kg, is:
A) 160
B) 180
C) 220
D) 240
Solution:-
Let the price of juice be Rs. $x$ per kg.
Since the cost price of syrup is 20% less than the cost price of juice, the cost price of syrup is $0.8x$ per kg.
Total cost price of syrup $= 110 × 0.8x = 88x$
Total cost price of juice $= 120 × x = 120x$
Total cost price $= 88x + 120x = 208x$
Since the overall profit percentage is 64%,
Total profit $= 0.64(208x) = 133.12x$
Profit generated by selling 10 kg of syrup which costs
Rs $0.8x$ per kg at 10% profit $= 0.1 ×10 ×0.8x = 0.8x$
Profit generated on selling 20 kg of juice which costs Rs $x$ per kg at 20% profit $= 0.2 ×20x = 4x$
The remaining profit $(133.12x - (0.8x + 4x) = 128.32x)$ is generated by selling 100 kg of syrup and
100 kg of juice at Rs 308.32 per kg.
The total selling price of 100 kg of syrup and 100 kg of juice is 200 × 308.32 = 2×(30832)
The cost price of 100 kg of syrup $= 0.8x ×100 = 80x$
Cost price of 100 kg of juice = $100x$
Total cost price $= 80x + 100x = 180x$
Profit = Selling price – Cost price
⇒ $128.32x = 2×(30832) - 180x$
⇒ $308.32x = 2×(30832)$
⇒ $x = 200$
Cost price of syrup per kg = 0.8 × (200) = Rs 160
Hence, the correct answer is option (1).
We suggest you 5 step key strategy to prepare numbers for CAT:
Step 1: Understand the weightage and question type of number system in CAT. Then break it into core concepts.
Step 2: Focus on building basic concepts like
Understanding of number properties
Quick methods to find squares, cubes, square roots, and cube roots
HCF and LCM
Factors and LCM
Remainders etc
Step 3: Learn the application of above discussed concepts in CAT
Step 4: Practice with CAT type questions. Take help from standard books as mentioned in Study resources in later section.
Step 5: Revise and learn short tricks
1. Arun Sharma: A Quantitative Approach for CAT (7th Edition)
2. Quantitative Aptitude for CAT by Nishit K Sinha
The candidates can download the various CAT preparation resources designed by Careers360 using the links given below.
eBook Title |
Download Links |
CAT 2025 Arithmetic Important Concepts and Practice Questions | |
CAT 2025 Algebra Important Concepts and Practice Questions | |
CAT 2025 Number System - Important Concepts & Practice Questions | |
CAT 2025 Exam's High Scoring Chapters and Topics | |
CAT Mock Test Series - 20 Sets, Questions with Solutions By Experts | |
Mastering CAT Exam: VARC, DILR, and Quant MCQs & Weightages | |
CAT 2025 Mastery: Chapter-wise MCQs for Success for VARC, DILR, Quant | |
CAT 2025 Quantitative Aptitude Questions with Answers | |
CAT 2025 Important Formulas | |
Past 10 years CAT Question Papers with Answers | |
CAT 2025 Quantitative Aptitude Study Material PDF - Geometry and Mensuration |
Frequently Asked Questions (FAQs)
Mostly questions are logic based but memorising the formula with logic may help you.
Well, as per my observation, these theorems are not al all required. Just focus on the basic concept and theorem.
In QA section, can expect around 3 – 4 questions from number system.
Important topics in Number System for CAT are:
HCF and LCM
To find trailing zeros
Factors
Unit digit and last two digits
Remainder theorem
Divisibility Rules
On Question asked by student community
The three key formulas that can solve almost all Profit & Loss problems are:
Profit/Loss % = (Profit or Loss / Cost Price) × 100%, where CP is the cost price.
Discount % = (Discount / Marked Price) × 100%, where MP is the marked price.
Mark up % = (Mark up Value / Cost Price) × 100%, where CP is the cost price.
These formulas can be adapted for problems involving discounts, marked price, or successive gains/losses.
For detailed examples and variations, you can from the article
With a 70 percent in CAT Examination, you can go for various B-Schools or private collages. The S. K. Patel Institute of Management in Gandhinagar is an option for those who score 70-80 percent in their CAT examination or The Gujarat Institute of Management (GIM) in Goa with a cutoff of 60-80 percentage. These are the collages you can look for in Gujarat or nearby.
Collage in other regions: BA Colleges Accepting 70-80 Percentile in CAT 2025
Thank You.
Hello dear candidate,
NO. your application for CAT will not rejected for wrong gender small mistake in the OBC NCL certificate. You will be considered as an OBC candidate.
you just need to get your OBC certificate corrected and need to inform the CAT helpdesk about this error.
Hello,
Here are some top MBA colleges in India with fees under Rs. 2 lakh and their exam/cutoff details:
SIMSREE, Mumbai – Fee around Rs. 1.3–1.4 lakh for 2 years. Accepts CAT, CMAT, MAH-CET, MAT, ATMA. Cutoff is very high, usually 99+ percentile in CAT/CMAT.
PUMBA (Dept. of Management Sciences, Savitribai Phule Pune University) – Fee around Rs. 1.2–1.3 lakh. Accepts CAT, CMAT, MAH-CET, ATMA. Cutoff approx. 75+ percentile in CAT, 90–95+ percentile in CMAT, high scores in MAH-CET.
TISS, Mumbai (MA HRM & other management-related programmes) – Fee around Rs. 1.7–1.9 lakh. Accepts CAT for some courses. Qualifying cutoff is around 60–70 percentile, but final selection cutoffs are higher.
These are the main government institutes where the full MBA/PG programme fee is within Rs. 2 lakh. Cutoffs vary slightly each year and by category, but SIMSREE and PUMBA generally need high scores, while TISS has its own process along with CAT shortlisting.
Hope it helps !
Hey! With a NEET score of 344 in the ST category, it is highly unlikely to get admission in any government BDS college in Delhi through the All India Quota. The cutoff for government BDS seats in Delhi usually falls around 400–450 for ST category, so your score is below that range.
You can consider private dental colleges, state quota seats in other states, or reattempt NEET next year to improve your chances.
Admissions Open | Globally Recognized by AACSB (US) & AMBA (UK) | 17.8 LPA Avg. CTC for PGPM 2025
AACSB, NBA & SAQS Accredited | H-CTC 41.55 LPA | Merit Based Scholarship
Ranked No. 3 Business School in India and no.35 in world by Financial Times MiM 2025 Ranking | Highest CTC: INR 89 LPA
1 Exam accepted by 17 Top Symbiosis Institutes for 29 MBA programmes.
IBSAT 2025-Your gateway to MBA/PGPM @ IBS Hyderabad and 8 other IBS campuses | Scholarships worth 10 CR
NAAC A++ Grade | MBA program graded A** (National) by CRISIL | AACSB, ACBSP and BGA Member