Question

Which number is a composite number? A.11 B.21 C.31 D.41

Answer 1

B. 21

Explanation:

31 is the only number that can be made by multiplying another number other than 1 and itself.

1x21=21

3x7=21

all the other options only have 2 factors

Answer 2

21

Explanation:

A prime number has only two factors: 1 and itself.

A composite number has more than two factors. The number 1 is neither prime nor composite.