abhasjha wrote:John would have reduced the time it took him to drive from his home to a certain store by 1/3 if he had increased his average speed by 15 miles per hour. What was John's actual average speed, in miles per hour, when he drove from his home to the store?
(A) 25
(B) 30
(C) 40
(D) 45
(E) 50
Since the time is reduced by 1/3, the faster time is 2/3 of the actual time.
Time and rate are RECIPROCALS.
2/3 of the actual time implies
3/2 of the actual speed.
In other words, John increased his speed by 50%.
Thus, the increase in the speed -- 15mph -- must be equal to 50% of the actual speed, implying that the actual speed = 30mph.
The correct answer is
B.
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