Several logs are stored in a pile with 18 logs on the bottom layer, 17 on the second layer, 16 on the third layer, and so on. If the top layer has one log, how many logs are in the pile?
A)162
B)171
C)153
D)170
E)none of the above

Question

Quizplus · Accepted Answer

The total number of logs in the pile is the sum of the logs in each layer. Using the formula for the sum of an arithmetic series, the number of logs in each layer can be found:
18 + 17 + 16 + ... + 1 = (18 + 1) / 2 x 18 = 171
Therefore, there are 171 logs in the pile.

Several Logs Are Stored in a Pile with 18 Logs