Eric has been donating books he no longer needs to his local library. After 3 months of donating, he had 157 books left in his room. After 8 months of donating, he had 102 books left in his room. How many books per month did Eric donate on average between months 3 and 8?

Question

ddcamp · Answer

In general:
$$Average=\frac{ Total }{ Time }$$

How many books did he donate in total?
How much time passed?

anonymous · Answer

Total books = 157+3x
Total books = 102+8x
So: 157+3x=102+8x$$\rightarrow 5x=55 \rightarrow x=11$$

anonymous · Answer

Each month 11, so between 3 and 8 months (I supoose not included, 4 months) 4x11=44

lovelycharm · Answer

thank you