Question

Eliza writes a number

- the number is between 20 and 30
-it has exactly 4 factors
-one of the factors is 7
what is Eliza’s number?

Answer 1

the answer is 21

Explanation:

if one of the factors is 7 and it's between 20 and 30

then it can be 21 or 28

7×3=21 and 7×4=28

now the factors of 21: 1, 3, 7, 21 (4 factors)

the factors of 28: 1, 2, 4, 7, 14, 28 (6 factors)

therfore 21 is the correct answer

Answer 2

The answer is twenty eight