Bunuel wrote:
Cars J and K are making the trip from City A to City B. Car J departs from City A 15 minutes after Car K does, and both cars travel along the same route. If Car K travels at a constant speed that is 80% the constant speed of Car J, then how many minutes will elapse before Car J catches up to Car K?
A. 20
B. 45
C. 60
D. 75
E. 1230
Are You Up For the Challenge: 700 Level QuestionsLet r = the speed of Car J, so 0.8r = the speed of Car K. Let’s also let t = Car J’s travel time, in hours; this means that (t + ¼) is Car K’s travel time (because 15 minutes = ¼ hour). We can create the equation:
Car K’s distance = Car J’s distance
(0.8r)(t + 1/4) = rt
0.8(t + 0.25) = t
0.8t + 0.2 = t
0.2 = 0.2t
1 = t
Since 1 hour = 60 minutes, choice C is the correct answer.
Answer: C
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