Question

Question #9a6c9

Answer 1

56

Explanation:

A composite number is a whole number with 3 or more factors.

Between 1 and 80 the composite numbers you can find are:

4, 6, 8, 9,
10, 12, 14, 15, 16, 18,
20, 21, 22, 24, 25, 26, 27, 28,
30, 32, 33, 34, 35, 36, 38, 39,
40, 42, 44, 45, 46, 48, 49,
50, 51, 52, 54, 55, 56, 57, 58,
60, 62, 63, 64, 65, 66, 68, 69,
70, 72, 74, 75, 76, 77, 78,

(1 and 80 are not included.)

That is a total of 56 numbers.

Answer 2

`56` composite numbers between `1 and 80`

Explanation:

Rather than trying to count all the composite numbers between 1 and 80, let's work it using other information

There are `78` numbers BETWEEN 1 and 80

There are 25 prime numbers up to 100.
The prime numbers between `80 and 100` are: `83,89,97`

There are therefore `22` prime numbers between 1 and 80.
`1` is neither prime nor composite..

So, of the `78` numbers, `22` are prime which means that `56` are composite.