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# How many of the numbers between 20 and 40 are prime numbers?

##### Administrator

**Staff member**

How many of the numbers between 20 and 40 are prime numbers?

A) 3

B) 4

C) 5

D) 6

E) 7

Recall that a prime number is a number that only has itself and 1 as a divisor.

- Remove all the evens since the are divisible by 2 (20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40)
- Remove all the remaining numbers divisible by 3 (21, 24, 27, 30, 33, 36, 39)
- Remove all the remaining numbers divisible by 5 (25, 35)

We're left with (**23, 29, 31, 37**)

This is 4 numbers which is answer **B**