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# If a car went the first third of the distance at 80 kmh, the

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If a car went the first third of the distance at 80 kmh, the [#permalink]

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05 Oct 2010, 12:20
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Difficulty:

55% (hard)

Question Stats:

67% (03:17) correct 33% (02:42) wrong based on 96 sessions

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If a car went the first third of the distance at 80 kmh, the second third at 24 kmh, and the last third at 48 kmh, what was the average speed of the car for the entire trip?

A. 36 kmh
B. 40 kmh
C. 42 kmh
D. 44 kmh
E. 50 kmh

(C) 2008 GMAT Club - m15#32
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Re: GMAT club Test m15#32 [#permalink]

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05 Oct 2010, 12:41
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AndreG wrote:
If a car went the first third of the distance at 80 kmh, the second third at 24 kmh, and the last third at 48 kmh, what was the average speed of the car for the entire trip?

(C) 2008 GMAT Club - m15#32

* 36 kmh
* 40 kmh
* 42 kmh
* 44 kmh
* 50 kmh

$$Average \ speed=\frac{total \ distance}{total \ time}$$, let the total distance be $$3x$$, then: $$total \ time=\frac{x}{80}+\frac{x}{24}+\frac{x}{48}=\frac{18x}{240}$$;

$$Average \ speed=\frac{total \ distance}{total \ time}=\frac{3x}{\frac{18x}{240}}=\frac{240*3}{18}=40$$.

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Re: GMAT club Test m15#32 [#permalink]

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05 Oct 2010, 12:44
Thanks! I confused distance with time and just couldnt wrap my head around where I went wrong
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Re: If a car went the first third of the distance at 80 kmh, the [#permalink]

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05 Oct 2014, 10:27
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Re: If a car went the first third of the distance at 80 kmh, the [#permalink]

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27 Jan 2015, 20:33
If a car went the first third of the distance at 80 kmh, the second third at 24 kmh, and the last third at 48 kmh, what was the average speed of the car for the entire trip?

A. 36 kmh
B. 40 kmh
C. 42 kmh
D. 44 kmh
E. 50 kmh

SOLUTION:

Assume D/3 = 240 (this number is convenient because it is divisible by 80, 24 and 48)

So:
240 = 80*T1 = 3 hrs
240 = 24*T2 = 10 hrs
240 = 48*T3 = 5 hrs

T = T1 + T2 + T3 = 18 hrs

D = RT
(240*3) = R*18
R = 40

Re: If a car went the first third of the distance at 80 kmh, the   [#permalink] 27 Jan 2015, 20:33
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