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

anonymous · Answer

-31 books per month

-18 books per month

-11 books per month

-7 books per month

phi · Answer

I would do:  (change in books) divided by (change in months)

anonymous · Answer

So, 55/5?

phi · Answer

yes, but simplify that

and strictly speaking if you did it in the order:  (3,157)  ,  (8, 52)
you would do  :  (157-52)/ (3 -8) = 55/-5
and you get a negative number.   but all your choices are negative, so you would still guess the correct answer (I hope)

anonymous · Answer

So the answer is C, -11?