so you want
40+39+38+...+1 or 1+2+3+...+39+40
a = 1, d = 1 for n=40
sum(40) = (40/2)(first + last)
= 20(1+40)
= 820
The Recycling Department of a fast food chain is planning to have a Christmas Tree Making Contest in preparation of the upcoming Holiday Season. Part of the contest mechanics is to collect soft drinks tin cans and build a Christmas Tree out of the tin cans. If you want to join the contest and plan to have 40 tin cans in the bottom row and one tin can fewer in each successive row. How many tin cans are there in your Christmas Tree?
1 answer
1 answer