What are the common factors of 21 and 45?

Answer 1

Method to find common factors:

Step 1: Find the difference between the two numbers.

52 - 42 = 10.

Step 2: Find the factors of the difference so obtained.

Factors of 10 are 1, 2, 5 and 10.

Step 3: Check with only factors.

1 is factor of every number so, 1 is one of the common factors.

42 and 52 both are even numbers so, 2 is also the common factor.

Numbers ending with the digit either 5 or 0 are only divisible by 5. And the ones ending with only 0 are divisible by 10.

Clearly 42 and 52 are not divisible by 5 and 10.

So, the only common factors of 42 and 52 are 1 and 2.

Answer 2

The common factors of 42 and 105 are: 1, 3, 7, and 21

Answer 3

1 and 3 are the common factors of 21 and 45

Answer 4

The only [non-trivial] common factor of 42 and 50 is 2.

Answer 5

The common factors are: 1, 2

Answer 6

Just 1

Answer 7

1 and 5

Answer 8

1 and 13

Answer 9

1,2,3 and 6