Use the formula for the sum of the first n integers to evaluate the sum given below (in Description).

Question

4 + 8 + 12 + 16 +    + 240

Answer 1

Gauss' formula for the sum of the numbers from 1 to n is: Sum = n(n+1)/2

4 + 8 + 12 + 16 +    + 240

First, note that this is:

4*1 + 4*2 + 4*3 +3*4 + ..... + 4*60 = 4 * ( 1+2+3+4+,,,+60)

Sum = 4 * 60*61/2

Sum = 7320