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If Alice traveled on a 10 km trip at a constant speed of 25

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If Alice traveled on a 10 km trip at a constant speed of 25

by Max@Math Revolution » Fri Jun 29, 2018 12:06 am

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[GMAT math practice question]

If Alice traveled on a 10 km trip at a constant speed of 25 km/h and a 48 km trip at a constant speed of 30 km/h, what was her average speed, in kilometers per hour, for the two trips?

A. 26 km/h
B. 28 km/h
C. 29 km/h
D. 30 km/h
E. 32 km/h
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by GMATGuruNY » Fri Jun 29, 2018 2:50 am
Max@Math Revolution wrote:[GMAT math practice question]

If Alice traveled on a 10 km trip at a constant speed of 25 km/h and a 48 km trip at a constant speed of 30 km/h, what was her average speed, in kilometers per hour, for the two trips?

A. 26 km/h
B. 28 km/h
C. 29 km/h
D. 30 km/h
E. 32 km/h
Since Alice travels only a small portion of the total distance at 25 kph but the vast majority of the entire distance at 30 kph, her average speed for the entire trip must be just a bit less than 30 kph.
Of the five answer choices, only C is sufficiently close to 30 kph.

The correct answer is C.
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by Max@Math Revolution » Sun Jul 01, 2018 4:59 pm
=>
The total time taken for the two trips is 10 / 25 + 48 / 30 = 0.4 + 1.6 = 2 hours.
The total distance traveled on the two trips is 10 + 48 = 58 km.
Thus, the average speed for the two trips is the total distance over the total time, or 58 / 2 = 29 km / h.

Therefore, the answer is C.
Answer: C
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by Scott@TargetTestPrep » Mon Apr 29, 2019 8:08 am
Max@Math Revolution wrote:[GMAT math practice question]

If Alice traveled on a 10 km trip at a constant speed of 25 km/h and a 48 km trip at a constant speed of 30 km/h, what was her average speed, in kilometers per hour, for the two trips?

A. 26 km/h
B. 28 km/h
C. 29 km/h
D. 30 km/h
E. 32 km/h
We can use the equation average rate = total distance/total time

average = 58/(10/25 + 48/30)

average = 58/(2/5 + 8/5)

average = 58/(10/5) = 58/2 = 29

Answer: C

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