Question

common factor of 20 and 32

Answer 1

Using prime factorisation,
Prime factors of 20 = 1 X 2 X 2 X 5.
Prime factors of 32 = 1 X 2 X 2 X 2 X 2 X 2.

Hence, the commons factors of 20 and 32 = 1 X 2 X 2 = 4