Solutions
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Question
A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 75 kilometers per hour. At what speed, in kilometers per hour, is the car traveling?
Option A:
71.5
Option B:
72
Option C:
72.5
Option D:
73
Option E:
73.5
Difficulty Level
HardSolution
Option B is the correct answer.
Option Analysis
75 kilometers per hour is the same as 75 kilometers per 60 minutes….
75/60 = 5/4 = 5 kilometers every 4 minutes
This means that every 1 kilometer takes 4/5 minutes = 48 seconds
We’re then asked to add 2 seconds to this and calculate the speed. 48 + 2 = 50 seconds
To find the speed, we can use a ratio (50 seconds = 5/6 minutes):
5/6 = 60 min/X kph
Cross multiply the ratio: 5X = 360
X = 72 kph
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