Answer:
10 books.
Step-by-step explanation:
(b) To estimate the mean we take the mean value of books for each bar.
So for 0-4 books we use 4/2 = 2, for 5-9 we use (9-5)/ 2 + 5 = 7 and so on for each bar. So the estimate for the first bar is 2 * 9 = 18 books.
So the required mean = total estimate of books bought / number of students
= (9 *2 + 10*7 + 12*13 + 17*2 + 22*6) / 40
= 410 / 40
= 10.25
