List of top Mathematics Questions on Common Factors and Common Multiples

Find first three common multiples of :

1) 6 and 8

2) 12 and 18

A number is divisible by both 5 and 12. By which other number will that number be always divisible?
Write the smallest 5-digit number and express it in the form of its prime factors.
Which factors are not included in the prime factorisation of a composite number?
The product of three consecutive numbers is always divisible by 6. Verify this statement with the help of some examples.
Find all the prime factors of 1729 and arrange them in ascending order. Now state the relation, if any; between two consecutive prime factors.
Write the greatest 4-digit number and express it in terms of its prime factors.
Here are two different factor trees for 60. Write the missing numbers.
A number is divisible by 12. By what other numbers will that number be divisible?

Which of the following numbers are co-prime?

  1. 18 and 35
  2. 15 and 37
  3. 30 and 415
  4. 17 and 68
  5. 216 and 215
  6. 81 and 16
Write all the numbers less than 100 which are common multiples of 3 and 4.
18 is divisible by both 2 and 3. It is also divisible by 2 × 3 = 6. Similarly, a number is divisible by both 4 and 6. Can we say that the number must also be divisible by 4 × 6 = 24? If not, give an example to justify your answer.

Find the common factors of :

1) 4, 8 and 12

2) 5, 15 and 25

Find the common factors of:

1) 20 and 28

2) 15 and 25

3) 35 and 50

4) 56 and 120