Between 10 and 20, the composite numbers are 10, 12, 14, 15, 16, 18, and 20. To find these numbers, let’s first clarify what a composite number is: a composite number is a positive integer that has at least one positive divisor other than one or itself, meaning it can be divided evenly by numbers other than 1 and itself.
Now, let’s analyze the numbers between 10 and 20:
- 10 (divisible by 1, 2, 5, 10)
- 11 (prime – only divisible by 1 and 11)
- 12 (divisible by 1, 2, 3, 4, 6, 12)
- 13 (prime – only divisible by 1 and 13)
- 14 (divisible by 1, 2, 7, 14)
- 15 (divisible by 1, 3, 5, 15)
- 16 (divisible by 1, 2, 4, 8, 16)
- 17 (prime – only divisible by 1 and 17)
- 18 (divisible by 1, 2, 3, 6, 9, 18)
- 19 (prime – only divisible by 1 and 19)
- 20 (divisible by 1, 2, 4, 5, 10, 20)
Counting the composite numbers, we have 10, 12, 14, 15, 16, 18, and 20, which totals to 7 composite numbers in this range.