ISEE Mathematics Achievement Question 298: Answer and Explanation

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Question: 298

10. Joe wants to find the mean number of pages in the books he has read this month. The books were 200, 220, and 260 pages long. He read the 200 page book twice, so it will be counted twice in the mean. If he reads one more book, what is the fewest number of pages it can have to make the mean no less than 230 ?

  • A. 268
  • B. 269
  • C. 270
  • D. 271

Correct Answer: C

Explanation:

C Since the question mentions the mean, create an Average Pie. . Joe wants to have an average of 230 or more, so place 230 in the average spot of the pie. In the # of items place, write in 5 because he has already read 4 books that were 200, 200, 220, and 260 pages long, and he is going to read one more. Multiply to find the total number of pages he must read: 5 × 230 = 1,150. He has already read 200 + 200 + 220 + 260 = 880 pages, so find the difference between these two totals to see how many pages long the fifth book must at least be: 1,150 - 880 = 270. The correct answer is (C).

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