Summation problem (first N positive integers)

1. Oct 5, 2013

GeorgeCostanz

1. The problem statement, all variables and given/known data

2. Relevant equations

so i kno the formula for the for the sum of the first N positive integers

when i = 1

3. The attempt at a solution

i kno the answer = n^2(n+1)/2

but could someone explain step by step how you reduce it to get the final answer? as if i'm in kindergarten? i'm slow, thanks.

my work:

following the formula: n(n+1)/2 * n(n+1)/2 * n(n+1)/2 ?

i don't understand how to reduce the terms to get the final answer provided

Last edited: Oct 5, 2013
2. Oct 5, 2013

Ray Vickson

PF rules require you to show us your work.

3. Oct 5, 2013

oh okay sure

4. Oct 5, 2013

rcgldr

Are you sure the upper bound on the second summation is "i" and not "n"? Note that this is a summation of the value "1", not the variable "i".

5. Oct 5, 2013

Dick

If the upper bound on the second summation were "n" then the sum would be n^3. You are only going to get the correct answer if the upper bound is "i". Start with the innermost sum and work your way out. It's not hard.