Question

If you can only use 3 of these numbers once to find a sum of 30 without subtracting or adding additional numbers, what three numbers would you use out of 1, 3, 5, 7, 9, 11, 13, and 15? ()+()+()=30

Answer 1

Answer: The answer is 7+(3+5)+15 = 30

Answer 2

The correct answer is

It is impossible to add odd numbers (1, 3, 5, 7, 9, 11, 13, and 15) and odd number of times (3) to get an even number (30)

Explanation:

1, 3, 5, 7, 9, 11, 13, and 15 are all odd numbers and 30 is an even number

When odd numbers are added even times the answer is always even for example 3 + 5 = 8, and when odd numbers are added odd times the answer is always odd for example 1 + 5 + 7 = 13

It is not possible to add three odd numbers to get an even number

Where x = odd therefore x + 1 = even = y say

hence 2 × x = 2×(y-1) = 2·y - 2 = even number

Also 3 × x = (3y -3) = odd number