Answer:
11 shelves.
Divide 96 by 9
96 ÷ 9 = 10.6
Since 10.6 rounds to 11, and it is more than 10, we will need 11 shelves to store the books, since there is no such thing as a half-bookshelf here.
0.35 you divide the 21 feet per second and the 60 seconds in a minute to get 0.35
Multiplied by 10 more each time