Which number in each group is not a prime number? 31,41, 51?

Hey there!

Your answer is 51.

First of all, a prime number is a number whose only factors are 1 and itself.

31 and 41 both fit the description of a prime number.

31's only factors are 1 and 31, and 41's only factors are 1 and 41.

However, in addition to 1 and 51, 51 has two other factors: 3 and 17.

This means that 51 is not a prime number.

Hope this helps!

51

Step-by-step explanation:

answer: 180

step-by-step explanation:

12-2=10

20-2=18

10x18=180