Question

Sum of the product of all odd numbers from 0 to 20 taking two at a time

Answer 1

Odd numbers from 0 - 20 are 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19.

So, (1 × 3) + (5 × 7) + (9 × 11) + (13 × 15) + (17 × 19) =

3 + 35 + 99 + 195 + 323 = 655

∴ the sum of the product of all the odd numbers from 0 - 20 taking two at a time (in ascending order) is 655.