Question

circle the composite numbers: 20 14 5 12 45 7 33 13 70 2 19 8 15 11

Explanation:

Step1: Recall composite number definition

A composite number has more than two factors.

Step2: Analyze 20

$20 = 1\times20=2\times10 = 4\times5$, so it's composite.

Step3: Analyze 14

$14=1\times14 = 2\times7$, so it's composite.

Step4: Analyze 5

$5 = 1\times5$, it has only two factors, so it's prime.

Step5: Analyze 12

$12=1\times12=2\times6 = 3\times4$, so it's composite.

Step6: Analyze 45

$45=1\times45=3\times15 = 5\times9$, so it's composite.

Step7: Analyze 7

$7 = 1\times7$, it has only two factors, so it's prime.

Step8: Analyze 33

$33=1\times33=3\times11$, so it's composite.

Step9: Analyze 13

$13 = 1\times13$, it has only two factors, so it's prime.

Step10: Analyze 70

$70=1\times70=2\times35 = 5\times14=7\times10$, so it's composite.

Step11: Analyze 2

$2 = 1\times2$, it has only two factors, so it's prime.

Step12: Analyze 19

$19 = 1\times19$, it has only two factors, so it's prime.

Step13: Analyze 8

$8=1\times8=2\times4$, so it's composite.

Step14: Analyze 15

$15=1\times15=3\times5$, so it's composite.

Step15: Analyze 11

$11 = 1\times11$, it has only two factors, so it's prime.

Answer:

20, 14, 12, 45, 33, 70, 8, 15