Exercise 53 Page 206

Let the number of logs in the top row be the first term and the logs in the bottom row be the last term in the sequence. Using this information we can write the endpoints of the sequence. We know that each row in the pile has one more log than the row above it. Therefore, when going from the top row to the bottom row we add one log for each row. This forms an arithmetic sequence with a common difference of $1.$

In order to find the total number of logs in the pile, we need to find the sum of the terms in this sequence. We can use a calculator to find the sum directly.

The number of logs in the pile is $119.$