A stack of poles has 36 poles in the bottom row, 35 poles in the next row, and so on, with 10 poles in the top row. How many poles are there in the stack?
A) 611
B) 555
C) 621
D) 631

Question

Quizplus · Accepted Answer

This is a sum of an arithmetic series where the first term, a = 36, the last term, l = 10, and the number of terms, n, can be found as n = 36 - 10 + 1 = 27 (since the series is decreasing, we subtract the last term from the first and add one to include both ends). The sum of the series, S, can be calculated using the formula S = n/2 * (a + l), which gives S = 27/2 * (36 + 10) = 621.

A Stack of Poles Has 36 Poles in the Bottom