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CBSE

Class 6 Important Question

Maths

Chapter 5: Understanding Elementary Shapes

CBSE Important Questions for Class 6 Maths Prime Time - 2025-26

Q: 3. From an exam perspective, what are the core topics to focus on within the Prime Time chapter?

To secure good marks, you should focus on mastering prime factorisation, as it is the foundation for other topics. Pay special attention to the methods for calculating HCF and LCM and understanding the difference in their application for word problems. Also, memorising prime numbers up to 100 is a valuable exam skill.

Q: 5. What is a common mistake students make when identifying prime numbers, and how can it be avoided in the exam?

A very common mistake is forgetting that the number 1 is neither prime nor composite. Another frequent error is incorrectly classifying numbers like 51 (3 x 17) or 91 (7 x 13) as prime. To avoid this, systematically check for divisibility by prime numbers (2, 3, 5, 7, 11) before concluding a number is prime. This methodical approach is key to accuracy in an exam.

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CBSE Important Questions for Class 6 Maths Prime Time - 2025-26

Vedantu’s CBSE Class 6 Maths Chapter 5 Prime Time Important Questions are prepared to help students practise effectively. You can also find our experts created extra questions that make understanding simple.

Each question is designed to match the CBSE Class 6 Maths Syllabus for better understanding. Start exploring our Class 6 Maths Important Questions and make your maths preparation better with Vedantu.

Important Questions for CBSE Class 6 Maths Chapter 5 - Prime Time

1. Find the prime factorisation of these numbers without multiplying first.
(a) 56 × 25
(b) 108 × 75
(c) 1000 × 81
Solution:
(a) Prime factors of 56 = 2 × 2 × 2 × 7
Prime factors of 25 = 5 × 5
Combined prime factorization of 56 × 25 = 2 × 2 × 2 × 7 × 5 × 5

(b) Prime factors of 108 = 2 × 2× 2 × 3 × 3
Prime factors of 75 = 3 × 5 × 5
Combined prime factorization of
108 × 75 = 2 × 2 × 3 × 3 × 3 × 3 × 5 × 5

(c) Prime factors of 1000 = 2 × 2 × 2 × 5 × 5 × 5
Prime factors of 81 = 3 × 3 × 3 × 3
Combined prime factorization of 1000 × 81 = 2 × 2 × 2 × 5 × 5 × 5 × 3 ×3 × 3 × 3

2. The prime factorization of a number has one 2, two 3s, and one 11. What is the number?

Solution:

To find the number, we multiply these prime factors together:

2 × 3 × 3 × 11 = 198

Thus, the number is 198.

3. Find the prime factorization of these numbers without multiplying first.
(a) 56 × 25
(b) 108 × 75
(c) 1000 × 81
Solution:
(a) Prime factors of 56 = 2 × 2 × 2 × 7
Prime factors of 25 = 5 × 5
Combined prime factorization of 56 × 25 = 2 × 2 × 2 × 7 × 5 × 5

(b) Prime factors of 108 = 2 × 2 × 2 × 3 × 3 × 3
Prime factors of 75 = 3 × 5 × 5
Combined prime factorization of
108 75 = 2 × 2 × 3 × 3 × 3 × 3 × 5 × 5

(c) Prime factors of 1000 = 2 × 2 × 2 × 5 × 5 × 5
Prime factors of 81 = 3 × 3 × 3 × 3
Combined prime factorization of 1000 × 81 = 2 × 2 × 2 × 5 × 5 × 5 × 3 × 3 × 3 × 3

4. The teacher asked if 14560 is divisible by all of 2, 4, 5, 8 and 10. Guna checked for divisibility of 14560 by only two of these numbers and then declared that it was also divisible by all of them. What could those two numbers be?
Solution:
If a number is divisible by 8, it will automatically be divisible by 4.
If a number is divisible by 10, it is also divisible by 2 and 5. Therefore, checking divisibility by 8 and 10 confirms divisibility by all other numbers (2, 4, 5).
Thus, the pair of numbers that Guna could check to determine that 14560 is divisible by all of 2, 4, 5, 8, and 10 is: 8 and 5.

5. What is the smallest number whose prime factorization has:
(a) three different prime numbers?
(b) four different prime numbers?
Solution:
(a) The smallest prime numbers are 2, 3, and 5. To find the smallest number with these primes as factors, multiply them together:
2 × 3 × 5 = 30
So, the smallest number whose prime factorization has three different prime numbers is 30.

(b) The smallest four prime numbers are 2, 3, 5, and 7. To find the smallest number with these primes as factors, multiply them together:
2 × 3 × 5 × 7 = 210

Thus, the smallest number whose prime factorization has four different prime numbers is 210.

6. Which of the following pairs of numbers are co-prime?
(a) 18 and 35
(b) 15 and 37
(c) 30 and 415
Answer:
(a) Here factors of 18 = 1 × 2 × 3 × 3 and factors of 35 = 1 × 5 × 7
No common factor other than 1.
Hence 18 and 35 are co-prime numbers.

(b) We have factors of 15 = 1 × 3 × 5 and factors of 37 = 1 × 37
No common factor other than 1.
Hence 15 and 37 are co-prime numbers.

(c) Given numbers are 30 and 415 Here factors of 30 = 1 × 2 × 3 × 5 and factors of 415 = 5 × 83
Clearly, 5 is a common factor of 30 and 415.
Hence 30 and 415 are not co-prime numbers.

7. Who am I?

(a) I am a number less than 40. One of my factors is 7. The sum of my digits is 8.

(b) I am a number less than 100. Two of my factors are 3 and 5. One of my digits is l more than the other.

Solution:

(a) 7 is the common factor of 7, 14, 21,28, 35, which are less than 40. And there is one number which has a digit sum of 8, is 35 = (3 + 5) = 8.

So, I am 35.

(b) Common factors of 3 and 5 are 15, 30, 45, 60, and 75,90, (which are less than 100). And there is one number one of the digits is 1 more than the other is 45. So, I am 45.

8. The prime factorization of a number has one 2, two 3s, and one 11. What is the number?

Solution:

To find the number, we multiply these prime factors together:

2 × 3 × 3 × 11 = 198

Thus, the number is 198.

9. Find the largest and smallest 4-digit numbers that are divisible by 4 and are also palindromes.

Solution:

Largest 4-digit number divisible by 4 and is also palindrome- 8888

The smallest 4-digit number is divisible by 4 and is also palindrome- 2112.

10. Consider these statements:

(a) Only the last two digits matter when deciding if a given number is divisible by 4.

(b) If the number formed by the last two digits is divisible by 4, then the original number is divisible by 4.

Do you agree? Why or why not?

Solution:

(a) Yes, that’s correct. When determining if a number is divisible by 4, only the last two digits of the number matter. This is because 100 is divisible by 4, so the divisibility rule for 4 focuses on whether the number formed by the last two digits is divisible by 4.

(b) Yes, that’s correct. If the number formed by the last two digits of a given number is divisible by 4, then the original number is also divisible by 4.

(c) Yes, that’s correct. If the original number is divisible by 4, the last two digits of the number will indeed be divisible by 4.

Check Out Some Extra Questions for More Practise

1. Find the prime factorization of these numbers without multiplying first.

(a) 84 × 45

Prime factors of 84 = 2 × 2 × 3 × 7

Prime factors of 45 = 3 × 3 × 5

Combined prime factorization: 2 × 2 × 3 × 3 × 3 × 5 × 7

(b) 126 × 64

Prime factors of 126 = 2 × 3 × 3 × 7

Prime factors of 64 = 2 × 2 × 2 × 2 × 2 × 2

Combined prime factorization: 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 7

2. A number has three 2s, two 5s, and one 7 in its prime factorization. What is the number?

Solution: Multiply the given prime factors together:

2 × 2 × 2 × 5 × 5 × 7 = 1400

Thus, the number is 1400.

3. Who am I?

(a) I am a number less than 50. One of my factors is 5, and the sum of my digits is 6.

Solution: Numbers less than 50 with 5 as a factor: 5, 10, 15, 20, 25, 30, 35, 40, 45

Checking digit sum:

15 → 1 + 5 = 6

So, I am 15.

(b) I am a number less than 200. Two of my factors are 2 and 3. One of my digits is twice the other.

Solution: Numbers divisible by 2 and 3 (i.e., divisible by 6): 12, 18, 24, 30, 36, 42, 48, 54, 60, 72, 84, 96, 102, 108, 120, 132, 144, 150, 162, 180, 192

Checking for a number where one digit is twice the other:

18 → 8 is not twice 1

24 → 4 is not twice 2

36 → 6 is twice 3

So, I am 36.

4. Which of the following pairs of numbers are co-prime?

(a) 22 and 35

(b) 42 and 65

Solution:

(a) Factors of 22 = 1, 2, 11, 22

Factors of 35 = 1, 5, 7, 35

No common factor other than 1 → Co-prime

(b) Factors of 42 = 1, 2, 3, 6, 7, 14, 21, 42

Factors of 65 = 1, 5, 13, 65

No common factor other than 1 → Co-prime

5. How many prime numbers are there from 21 to 30?

Solution: In total, there are 2 prime numbers between 21 and 30.

They are 23 and 29.

6. How many composite numbers are there from 21 to 30?

Solution: The total number of composite numbers from 21 to 30 is 8.

They are 21,22,24,25, 26, 27, 28, 30.

This page consists of a different set of short question answers to help students practice effectively. These short question answers will help to solve any kind of problem based on numbers. Use them to improve your understanding and score better on your test papers.

Download our CBSE Class 6 Maths CHapter 5 Prime Time Important Question and start practising now!

Important Study Materials for Class 6 Maths Chapter 5 Prime Time

S.No	CBSE Class 6 Maths Chapter 5 Other Study Materials
1	CBSE Class 6 Maths Prime Time Notes
2	CBSE Class 6 Maths Prime Time Solutions

CBSE Class 6 Maths Chapter-wise Important Questions

S.No	Chapter-wise Important Questions for Class 6 Maths
1	Chapter 1 Patterns in Mathematics Questions
2	Chapter 2 Lines and Angles Questions
3	Chapter 3 Number Play Questions
4	Chapter 4 Data Handling and Representation Questions
5	Chapter 6 Perimeter and Area Questions
6	Chapter 7 Fractions Questions
7	Chapter 8 Playing with Constructions Questions
8	Chapter 9 Symmetry Questions
9	Chapter 10 The Other Side of Zero Questions

Important Related Links for CBSE Class 6 Maths

S.No	Related Study Materials for Class 6 Maths
1.	CBSE Class 6 Maths NCERT Book
2.	CBSE Class 6 Maths NCERT Solutions
3.	CBSE Class 6 Maths Notes
4.	CBSE Class 6 Maths Sample Papers
5.	CBSE Class 6 Maths Worksheets
6.	CBSE Class 6 Maths Formulas
7.	CBSE Class 6 Maths NCERT Exemplar
8.	CBSE Class 6 Maths RS Aggarwal Solutions
9.	CBSE Class 6 Maths RD Sharma Solutions

FAQs on CBSE Important Questions for Class 6 Maths Prime Time - 2025-26

1. How can practising important questions from Chapter 5, Prime Time, improve my exam score?

Practising important questions for Class 6 Maths Chapter 5 helps you master key concepts for the 2025-26 exam. It improves your problem-solving speed and accuracy, familiarises you with frequently asked question formats, and helps you learn how to apply concepts like HCF and LCM effectively to score higher marks.

2. What types of questions are considered most important from the Class 6 Maths chapter, Prime Time?

For the Prime Time chapter, the most important types of questions for your exam include:

Identifying prime and composite numbers within a given range.
Finding the prime factorisation of a number using the factor tree or division method.
Calculating the HCF (Highest Common Factor) and LCM (Lowest Common Multiple) of two or more numbers.
Solving word problems based on real-life applications of HCF and LCM.

3. From an exam perspective, what are the core topics to focus on within the Prime Time chapter?

To secure good marks, you should focus on mastering prime factorisation, as it is the foundation for other topics. Pay special attention to the methods for calculating HCF and LCM and understanding the difference in their application for word problems. Also, memorising prime numbers up to 100 is a valuable exam skill.

4. Why is finding the HCF and LCM of numbers such an important skill for Class 6 exams?

Understanding HCF and LCM is critical because these concepts are frequently tested through application-based word problems. HCF is used for problems involving splitting things into smaller sections or arranging them in groups (e.g., finding the largest size of tile to cover a floor). LCM is used for problems about events repeating at different intervals (e.g., finding when two bells will ring together). Mastering this shows the examiner you can apply maths to real situations.

5. What is a common mistake students make when identifying prime numbers, and how can it be avoided in the exam?

A very common mistake is forgetting that the number 1 is neither prime nor composite. Another frequent error is incorrectly classifying numbers like 51 (3 x 17) or 91 (7 x 13) as prime. To avoid this, systematically check for divisibility by prime numbers (2, 3, 5, 7, 11) before concluding a number is prime. This methodical approach is key to accuracy in an exam.

6. Are there any HOTS (Higher Order Thinking Skills) questions that can be expected from the Prime Time chapter in the 2025-26 exam?

Yes, you can expect HOTS questions from this chapter. These are typically multi-step word problems that require you to first decide whether to use HCF or LCM, and then perform the calculation correctly. For example, a question might ask for the least number of square tiles needed to pave a rectangular courtyard, which requires you to first find the HCF of the dimensions to determine the tile size.

7. How can the concept of prime factorisation be applied to quickly solve complex problems in the exam?

Prime factorisation is a powerful tool that simplifies finding HCF and LCM for large numbers, saving valuable time in an exam. By breaking numbers down into their prime factors, you can easily identify the common factors for HCF and the highest power of all factors for LCM. This method is much faster and less error-prone than listing out all factors or multiples, especially for complex questions.

8. How do these important questions for 'Prime Time' differ from regular textbook exercises?

Textbook exercises are designed to build your foundational understanding of a single concept at a time. In contrast, these important questions are focused on exam applicability. They often integrate multiple concepts (e.g., using divisibility rules to speed up HCF), highlight common student errors, and mirror the language and complexity of actual CBSE exam papers, which is crucial for exam preparedness and scoring well.