jack0997 wrote:Jeff drives three times farther in 36 minutes than what Amy drives in 30 minutes. If Jeff drives at a speed of 40 miles per hour, at what speed, in miles per hour, does Amy drive?
(A) 6
(B) 9
(C) 16
(D) 24
(E) 32
Jeff drives three times farther in 36 minutes than what Amy drives in 30 minutes.
To determine the ratio of Jeff's speed to Amy's speed, plug in easy values.
Let Amy's speed = 1 mile per 30 minutes.
Since Jeff drives three times farther in 36 minutes, Jeff's speed = 3 miles per 36 minutes.
Convert the two speeds to miles per hour:
Amy = 1 mile per 30 minutes = 2 miles per 60 minutes =
2 miles per hour.
Jeff = 3 miles per 36 minutes = 1 mile per 12 minutes = 5 miles per 60 minutes =
5 miles per hour.
The values in blue imply that Mary's speed is 2/5 of Jeff's speed.
Since Jeff's actual speed = 40mph, we get:
Mary's actual speed = (2/5)(40) = 16mph.
The correct answer is
C.
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