Eighty runners took part in a cross country race. Their times are summarized in

Question

Eighty runners took part in a cross country race. Their times are summarized in the table below. (The cumulative relative frequencies refer to the proportions of runners whose times were less than or equal to the times given.) How many runners had times that were more than 20 minutes and at most 22 minutes? (A) 10 (B) 20 (C) 30 (D) 40 (E) 50 Which of the following could be the interquartile range of the times? (A) 3 minutes, 50 seconds (B) 4 minutes, 40 seconds (C) 8 minutes, 20 seconds (D) 10 minutes, 30 seconds (E) 12 minutes, 10 seconds

Explanation / Answer

18:

The probability that runner have time that was more than 20 minutes and at most 22 minutes is

0.5125 - 0.2625 = 0.25

So requried number of runners is

0.25 *80 = 20

Hence, option B is correct.

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