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04 May 2021, 05:24
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
79% (01:35) correct
21%
(00:47)
wrong
based on 68
sessions
History
Date
Time
Result
Not Attempted Yet
Hannah covers half of the distance between her house and office at 6 miles per hour and covers the rest of the distance at 10 miles per hour. What is the average speed, in miles per hour, of the entire journey?
A. 7.5
B. 8
C. 8.5
D. 9
E. 9.5
A. 7.5
B. 8
C. 8.5
D. 9
E. 9.5
04 May 2021, 22:22
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QuantMadeEasy
Let the total distance between Hannah's house and office = d miles
Average Speed = Total Distance/Total Time taken
Time taken to cover half distance at 6 miles per hour = \(\frac{d}{2}/6 = \frac{d}{12}\) hours
Time taken to cover remaining half distance at 10 miles per hour = \(\frac{d}{2}/10 = \frac{d}{20}\) hours
Total time taken =\(\frac{d}{12} + \frac{d}{20} = \frac{2d}{15}\) hours
Average speed = \(d/(\frac{2d}{15}\)) = \(\frac{15}{2}\) = 7.5 miles per hour
So, correct answer is option A.
04 May 2021, 22:51
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Average speed as distance traveled is constant: Find H.M. of the values: \(\frac{2 * 6 * 10 }{ 6 + 10} = \frac{120 }{ 16} = 7.5\)
Answer A
Answer A
