Question

Four positive whole number add up to 39

One of the number is a multiple of 7
The other three number are equal
Work out the result when the four number are multiplied

Answer 1

The answer is 4,536

Explanation:

7x + 3y = 39

Let's try x=1, 2, 3, ...

x=1

7 + 3y = 39

3y = 32

y is not a whole number.

x=2

14 + 3y = 39

3y = 25

y is not a whole number.

x=3

21 + 3y =39

3y = 18

y=6

So 21 * 6 * 6 * 6 = 4,536