Question

a library loans out 3 books every day for a week and no books are returned. the equation below is written to represent the situation: (-3)·7 = -21 which description best explains the meaning of -21 in the equation? a books were loaned out for -21 days. b the library now has -21 books. c the change in the number of books at the library over the course of the week was -21. d the number of books loaned per day was -21.

Explanation:

Step1: Analyze Option A

Days can't be negative. So A is wrong.

Step2: Analyze Option B

Number of books can't be negative in this context. So B is wrong.

Step3: Analyze Option C

Since 3 books are loaned out each day ($-3$ per day) for 7 days, the total change is $(-3)\times7=-21$. This means a decrease (change) of 21 books. So C is correct.

Step4: Analyze Option D

Number of books loaned per day is 3, not $-21$. So D is wrong.

Answer:

C. The change in the number of books at the library over the course of the week was $- 21$.