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CAT Number System, HCF & LCM Questions, LR & DI | Day 6 Preparation for CAT 2025
Edited By Irshad Anwar | Updated on Jun 18, 2025 05:20 PM IST | #CAT
HCF and LCM are key topics in the CAT Quantitative Ability section, forming a significant and frequently tested part of the Number System syllabus. These concepts require a thorough understanding, strategic practice, and quick problem-solving skills to excel. As part of the Day 6 preparation strategy for CAT 2025, this article focuses on effective methods and shortcuts to master HCF and LCM questions, helping aspirants strengthen their fundamentals, boost accuracy, and improve overall speed for a higher CAT score. Consistent practice and conceptual clarity in these areas can greatly enhance your performance in the exam.
Part-1: Quantitative Aptitude for CAT 2024
Topic: Number System questions for CAT (HCF and LCM CAT questions) Highest Common Factor (HCF and LCM / GCD):
HCF is the highest common divisor which divides two (or more) numbers completely.
For Example,
12 is HCF of 36 and 48.
17 is HCF of 340 and 357
3 x 22 is LCM of (3x 24 and 33 x 22)
The most common ways of finding HCF are
Prime Factorization Method:
Eg: To find HCF of 27 and 36
27 = 33
36 = 22 x 32
HCF = 32
Division Method:
Eg: To find HCF of 27 and 36
Divide 36 by 27; the remainder is 9
Divide 27 by 9; the remainder is 0.
(This process is repeated till the remainder is 0)
Least Common Multiple (LCM):
The least value which is divisible by two or more values completely, is LCM.
For Example:
72 is LCM of 8 and 9.
2184 is LCM of 8, 13 and 21.
33 x 24 is LCM of (3x 24 and 33 x 22)
The most common way of finding LCM is
Prime Factorization Method:
Eg: To find LCM of 27 and 36
27 = 33
36 = 22 x 32
LCM = 22 x 33
HCF and LCM questions, CAT Number System Questions From CAT Previous Year Papers/ HCF and LCM questions for CAT exam
The two previous year CAT questions on number system (HCF and LCM)are given below:
Q1. How many pairs of positive integers x, y exist such that HCF of x, y = 18 and product of x and y = 1620? [ CAT Question Paper]
2
8
1
3
Solution: C
Let the two numbers be 18a and 18b where a and b are co-prime numbers.
Also, 18a x 18b = 1620
So, a x b = 1620/ (18 x 18) = 5
Therefore, (a, b) = (1, 5); the only possible pair in a and b.
Q2. A red light flashes three times per minute and a green light flashes five times in 2 min at regular intervals. If both lights start flashing at the same time, how many times do they flash together in each hour? [CAT Question Paper ]
30
24
20
60
Solution: A
Red light flashes after every 60/3=20 sec
Green light flashes after every 120/5=24 sec
Both lights will flash together if the multiples of flushing times are common
i.e. LCM (20,24) =120 sec = 2min
Thus, both lights will flash together at intervals of 120 sec= 2 minute
In 1 hour, both lights flash together 60/2 = 30 times.
Prerequisite:
To prepare for the number system for CAT exam, students must have knowledge of:
Prime, composite, and Co-primes
Factors
Multiples
CAT 2025: VARC, DILR, and Quant MCQs & Weightages
Comprehensive CAT prep guide with focused practice on Verbal Ability, Data Interpretation & Logical Reasoning, and Quantitative Aptitude.
Download NowTips On CAT Preparation For Number System (HCF and LCM ):
The smallest number which when divided by a, b and c leaves a remainder R in each case then the number will be (L.C.M of a, b, c) + R.
The greatest number which divides a, b and c to leave the remainder R is H.C.F of (a – R), (b – R) and (c – R)
The greatest number which divide x, y, z to leave remainders a, b, c respectively is
H.C.F of (x – a), (y – b) and (z – c)
LCM of (a/b, c/d, e/f) = LCM (a, c, e)/ HCF (b, d, f)
HCF of (a/b, c/d, e/f) = HCF (a, c, e)/ LCM (b, d, f)
Practise different kinds of problems.
HCF of a and b × LCM of a and b = a × b
Apply the concepts to practise HCF and LCM questions.
Practise previous year CAT questions on number systems and LCM and HCF problems.
References to Study (Theory):
Learn the concept of HCF and LCM from class 10 Mathematics NCERT (For Theory)
Arun Sharma: A Quantitative Approach for CAT (6th Edition)
2iim Online Learning Classroom
References to Study (Practice):
MASTER Number System for CAT and GMAT by Nishit K Sinha.
Sample Papers
CAT previous year papers
Part-2: Logical Reasoning and Data Interpretation
Topic: Data Interpretation (Spider/ Radar Graph)
In previous articles-Day 5, strategies for DI based on Bar graph, Pie chart, Table graph and Line graph have been discussed. A different kind of DI on spiders will be discussed in this article for the CAT exam. Data interpretation is a must-come topic in the CAT Exam and other management entrance exams.
DI on Spider (Radar) Graph
It consists of equiangular spokes and each spoke represents one variable. These charts contain 0 at its centre.
This is a spider chart for 5 variables.
A=70
B=58
C=5
D=15
E=25
Blue line shows the value of a commodity on 5 different parameters.
Questions Based On Spider Graph From CAT Previous Year Papers
Five vendors are being considered for a service. The evaluation committee evaluated each vendor on six aspects – Cost, Customer Service, Features, Quality, Reach, and Reliability.
Each of these evaluations are on a scale of 0 (worst) to 100 (perfect). The evaluation scores on these aspects are shown in the radar chart. For example, Vendor 1 obtains a score of 52 on Reliability, Vendor 2 obtains a score of 45 on Features and Vendor 3 obtains a score of 90 on Cost. [CAT Question Paper 2019- slot 1]
Q1. On which aspect is the median score of the five vendors the least?
Customer Service
Cost
Reliability
Quality
Ans: (1)
The median is the mid-value. For all six parameters median is as follows:
Reliability=52-53
Reach=65
Quality=62
Features=55
Customer Service = 50 (least)
Cost =75
Q2. A vendor's final score is the average of their scores on all six aspects. Which vendor has the highest final score?
Vendor 1
Vendor 2
Vendor 3
Vendor 4
Ans: (2)
Total Score of Vendors:
Vendor 1 = (52+ 80+ 73+ 40 + 55 + 75) = 375
Vendor 2 = (40+ 58+ 70+ 45 + 42 + 80) = 335
Vendor 3 = (75+ 66+ 60+ 50+ 55+ 90) = 396
Vendor 4 = (25+ 45+ 40+ 90+ 70+ 70) = 340
Vendor 3 has the highest total and hence the highest average.
Q3. A list of all the vendors who are among the top three vendors on all six aspects is?
None of the Vendors
Vendor 1
Vendor 3
Vendor 1 and Vendor 3
Ans: (3)
Vendors in top 3 in each aspect:
Reliability = Vendor 3, Vendor 5 and Vendor 1
Reach = Vendor 1, Vendor 5, Vendor 3
Quality = Vendor 1, Vendor 2, Vendor 3
Features= Vendor 4, Vendor 5, Vendor 3
Customer Service = Vendor 4, Vendor 1, Vendor 3
Cost = Vendor 3, Vendor 2, Vendor 1
Clearly only vendor 3 appears in all the three.
Prerequisite:
To Prepare Data Interpretation (Spider graph) for the CAT 2024, a student must learn:
Percentage (Basic)
Simplification and approximation
Mean, Mode and Median
Observational Skills
References to Study (Theory):
LRDI for CAT and GMAT by Nishit K Sinha.
Crack XAT YouTube Channel
References to Study (Practice):
https://online.2iim.com
How to Prepare for Data Interpretation for CAT by Arun Sharma
CAT previous year papers
Part-3: VARCTopic: Articles And Its Uses
Article is one of the parts of speech in English grammar which is used to modify the Noun entities.
Indefinite Articles (A and An): Used with singular nouns only.
Examples:
An honest man.
A tall man.
Tomorrow a man will come to see you.
Definite Article (The): Refers to specific nouns and can be used with both singular and plural nouns.
Examples:
The man on dice is my ideal.
The Bible.
Practice Questions On Articles
Direction: Choose the correct article
Q.1 Who is _________ of England now.
the prime minister
a prime minister
Ans: A
Q2. There is _________ restaurant near my house.
a nice
nice
- Ans: A
Q3. My grandparents live in _____________ of the city
south
the south
Ans: B
Q4. Is this _____________ Australian breed?
a
an
Ans: B
Prerequisite:
Knowledge of Verbal sound.
Knowledge of Noun (singular and Plural)
CAT Preparation Tips To Prepare Articles And Its Uses
Articles do not use uncountable nouns.
Learn the specific cases where articles should not be used
Ex: Let’s go out for dinner tonight. (Incorrect)
Let’s go out for dinner tonight. (Correct)
Articles should not be used with pronouns.
Use no Article before names of sports, subjects, nationalities, and languages.
Develop reading habits.
Practice more and more exercises.
References to Study (Theory):
Advanced English grammar by Wren and Martin (Oxford)
engvid.com (YouTube channel as well as Web)
References to Study (Practice):
Questions bank from iquanta.com
Oxford Practice Grammar (sixth edition)
How to Prepare for Verbal Ability & Reading Comprehension for CAT by Meenakshi Upadhyay and Arun Sharma (9th Edition)
HCF LCM Question Weightage for CAT Exam
The HCF and LCM topic consistently appears in the CAT exam, with around 2 questions each year from 2020 to 2024. Mastering these concepts is crucial for scoring well in the Quantitative Aptitude section and improving overall performance and CAT marks.
Year | Topic Name | Number of Questions |
2020 | HCF and LCM | 2 |
2022 | HCF and LCM | 2 |
2023 | HCF and LCM | 2 |
2024 | HCF and LCM | 2 |
Short Tricks to Crack LCM HCF Questions for CAT 2025
LCM and HCF questions are quick to solve once you master a few smart tricks. These concepts are based on number properties and often appear in the CAT Quantitative Aptitude section. Use the shortcuts below to solve such questions faster and with greater accuracy.
1. Prime Factorisation Method
Trick:
Break numbers into their prime factors.
LCM = Product of the highest powers of all primes
HCF = Product of lowest powers of common primes
Example:
Find LCM and HCF of 12 and 18.
12 = 2² × 3
18 = 2 × 3²
LCM = 2² × 3² = 36
HCF = 2 × 3 = 6
2. Product Rule
Trick:
For two numbers:
LCM × HCF = Product of the numbers
Example:
Find LCM if HCF of 8 and 32 is 8.
Product = 8 × 32 = 256
LCM = 256 ÷ 8 = 32
3. Co-Prime Shortcut
Trick:
If two numbers are co-prime (HCF = 1),
LCM = Product of the numbers
Example:
Find LCM of 5 and 12
Since HCF(5,12) = 1 → LCM = 5 × 12 = 60
4. Euclidean Algorithm for HCF
Trick:
Use repeated division
HCF(a, b) = HCF(b, a % b)
Example:
Find the HCF of 48 and 18
48 % 18 = 12
18 % 12 = 6
12 % 6 = 0 → HCF = 6
5. HCF and LCM of Fractions
Trick:
HCF of fractions = HCF of numerators / LCM of denominators
LCM of fractions = LCM of numerators / HCF of denominators
Example:
Find HCF of 2/5 and 4/15
HCF(2, 4) = 2
LCM(5, 15) = 15
HCF = 2 / 15
6. Work Backwards Using Product Rule
Trick:
If LCM or HCF is given, use options and check if:
LCM × HCF = Product of numbers
Example:
If HCF = 4 and LCM = 60, find the pair.
Check options like (12, 20): 12 × 20 = 240;
LCM × HCF = 60 × 4 = 240
We will be back with Day-7 strategy tomorrow at the same time. keep practising and be focused. Students can practice number system mock test for CAT and can also practice DILR and VARC alongside as well.
Frequently Asked Questions (FAQs)
1. How important is the HCF and LCM topic for CAT 2025?
HCF and LCM consistently appear in CAT with 2 questions yearly. Mastering this topic helps solve problems quickly, boosting your score in the Quantitative Aptitude section.
2. What are the best methods to solve HCF and LCM questions efficiently?
Use prime factorisation, the product rule (LCM × HCF = product), and the Euclidean algorithm for quick calculations. Practice regularly to improve speed and accuracy.
3. How many questions on average are asked about HCF and LCM in CAT exams?
On average, CAT features 2 questions from HCF and LCM each year, making it a reliable scoring topic for candidates who prepare well.
4. Can HCF and LCM questions be tricky, or are they mostly straightforward?
Most HCF and LCM questions are simple but can be combined with other concepts like ratios or time-speed-distance, requiring careful analysis and practice.
5. How can I practice HCF and LCM questions effectively for CAT?
Solve previous years’ questions, use online quizzes, and apply shortcuts regularly. Focus on understanding concepts deeply and practising mixed problem sets for better performance.
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Questions related to CAT
Have a question related to CAT ?
Hello aspirant,
The question papers for CAT MGU University can be found on their official website, or you can also visit careers360 website for the same.
The link of which, I am attaching here,
https://university.careers360.com/articles/mgu-cat-2025
Regards
Mansi Satwani 07 July,2025
Hello Anshuman!!!
You have gotten 86% in 10th, which is a good score. 70% in graduation is not the best but decent. But the main problem is your 12th score which is 62%.
You would be already aware that the Top IIMs (BLACKI) give a big emphasis on your academic score. Let me tell you one example of IIM Ahmedabad,
According to a research i read a few days ago, in IIM Ahmedabad,
70.8%
of students has 90+ percent in 12th,
25.8%
has 80-90 percent and around
3.8%
has less than 80% with the bracket of 60-69 having only
0.26%
students of the total batch. Nearly same is the case of the other top IIMs like IIM Bangalore, IIM Calcutta, IIM Lucknow, IIM Kozhikode and IIM Indore.
Statistically, getting into these TOP IIMs is possible with 62% in 12th is possible (0.26% has done it) but practically you cannot get into these TOP IIMs unless you top the CAT exam.
See, I don't wish to dishearten or demotivate you but I wish to tell you the truth. Although the probability of you getting into these TOP IIMs is very less, but trying is better than doing nothing. You have a good score in 10th which will certainly help you. The least you could do is try your best.
My advice would be that you should not focus on these things like "Will I get top IIM" or negative talk like " I got low marks I won't qualify" etc.
The main focus should be on your preparation.
Give 100% in your preparation because that's the only thing in your hand. You can't change your 10th/12th/Graduation scores but you can put some more effort in your preparation which would certainly help to get better percentile.
Keep working hard and give your best. You might surprise yourself!!! And if not BLACKI, there are many other good colleges like FMS, MDI, newer IIMs etc.
Yash Teotia 06 July,2025
Hello,
Yes, with a 622 rank in IPU CET for MBA and being a Delhi candidate, you have a good chance of getting admission in MAIT (Maharaja Agrasen Institute of Technology).
You don’t need to worry about not giving the CAT exam. IPU CET rank is enough for admission in MAIT under the CET quota.
Just make sure to keep MAIT high in your preference list during counselling.
Hope it helps !
Prachi Kumari 04 July,2025
Hello,
A NEET 2025 score of 333 marks, an All India Rank (AIR) near 3,56,000, and belonging to the SC category from Andhra Pradesh suggest a fair possibility of obtaining an MBBS seat within the state quota, especially in private medical colleges under Category A (government quota seats in private institutions).
In Andhra Pradesh, SC category cut-offs for Category A seats in private institutions generally vary from 320 to 370, influenced by the college and the counselling round. Government medical colleges tend to be more competitive, with the SC cut-off for MBBS frequently rising, often exceeding 400 marks.
Although obtaining a government MBBS seat is improbable, you stand a feasible opportunity in private medical colleges within A category (which offer lower tuition than B and C categories). In Round 2 or the Mop-Up round, you can anticipate improved opportunities, since cut-offs generally decrease when other students move to superior colleges or vacate seats.
Colleges such as NRI Medical College (Guntur), Katuri Medical College (Guntur), Great Eastern Medical School (Srikakulam), Alluri Sitarama Raju Academy of Medical Sciences (Eluru), and Fathima Institute of Medical Sciences (Kadapa) are among those where seats could become available for SC students in subsequent rounds under Category A.
Hope this helps. All the best!
Samriddha Pal 08 July,2025
Yes, candidates who qualify in CUSAT CAT can gain admission to various participating institutes based on their rank. These include engineering colleges associated with CUSAT, such as its own School of Engineering in Kochi, Model Engineering College, and over 20 government and private engineering colleges across Kerala like College of Engineering Thrikkaripur, Co-operative Institute of Technology Vadakara, and MG College of Engineering Thiruvallam. The final seat allotment is based on your rank and your choice of program during the counselling process.
Pradeepa P 02 July,2025
Popular CAT Questions
Directions for question :
M/s Deloitte Touche Tohmatsu Limited, one of the top four audit and accounting firms in the world with headquarters at London, UK, and with an operational presence in 153 countries, hires Management Trainees (MT) from all the premier management institutes of India thrice every year, in the months of January, May and September.
Each new group of Management Trainees (MT) have to go through a four month rigorous training schedule, after which they have to pass through a test consisting of a written assessment and a case-analysis. The top hundred ranked Management Trainees (MT) based on the performance in the test are confirmed as Management Executives (ME). The rest are given the opportunity of undergoing the training for four months one more time along with the next batch of Management Trainees (MT) and then passing through the subsequent test consisting of the written assessment and case-analysis. The Management Trainee (MT) who fails to get confirmed as a Management Executive (ME) the second time is fired.
The scatter-graph below depicts the number of Management Trainees (MT) at Deloitte taking the tests from January 2020 till May 2022, and the vis-à-vis hired Management Trainees (MT) at Deloitte who were fired :
It is also known that for the month of September 2019 at Deloitte, 96 hired Management Trainees (MT) failed to be confirmed as a Management Executive (ME) the first time, and that 36 hired Management Trainees (MT) were fired.
Question :
In which test did the minimum number of Management Trainees (MT) get confirmed as a Management Executive (ME) in the second attempt ?
Option: 1
September 2020
Option: 2
May 2021
Option: 3
January 2021
Option: 4
January 2022
Directions for question:
The bar-graph given below shows the foreign exchange reserves of Nepal (in million Rupees) from 2014 to 2021. Answer the following questions based on the graph :
Question:
What was the percentage increase (rounded to the nearest integer, if deemed necessary) in the foreign exchange reserves in 2020 over 2016 ?
Option: 1 None
Option: 2 None
Option: 3 None
Option: 4 None
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