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 situ
(-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 each option

• Option A: Days cannot be negative in this context. The number of days is 7 (a positive value). So, this option is incorrect.
• Option B: The number of books in a library cannot be negative in a real - world sense. The negative sign here represents a decrease, not a negative quantity of books. So, this option is incorrect.
• Option C: Since 3 books are loaned out each day (\(- 3\) represents the change per day, negative because books are leaving the library) and over 7 days, the total change in the number of books is \((-3)\times7=-21\). This means the change in the number of books at the library over the week is \(-21\) (a decrease of 21 books).
• Option D: The number of books loaned per day is 3, and \(-3\) represents the change (loaning out) per day, not \(-21\). So, this option is incorrect.

Answer:

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