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# Mr. Jones drove from Town A to Town B in x hours. On the

Author Message
Director
Joined: 12 Jun 2006
Posts: 532
Mr. Jones drove from Town A to Town B in x hours. On the [#permalink]

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17 Sep 2007, 20:12
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Mr. Jones drove from Town A to Town B in x hours. On the return trip over the same route, his average speed was twice as fast. Which of the following expresses the total number of driving hours for the round trip?

(A) 2x/3
(B) 3x/2
(C) 5x/3
(D) 2x
(E) 3x
Director
Joined: 08 Jun 2007
Posts: 573

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17 Sep 2007, 20:14
ggarr wrote:
Mr. Jones drove from Town A to Town B in x hours. On the return trip over the same route, his average speed was twice as fast. Which of the following expresses the total number of driving hours for the round trip?

(A) 2x/3
(B) 3x/2
(C) 5x/3
(D) 2x
(E) 3x

B
Simple while coming since speed was double time taken was half the original x/2
So total time x+ x/2 = 3x/2
Manager
Joined: 29 Aug 2007
Posts: 110

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17 Sep 2007, 20:35
You cannot add rates in Motion problems. you can only add rates in Work / rate problems

Given this ,

Onward

rate = r

time =x

distance = rx

Toward

rate = 2r

time = t2
distance = rx

you can solve for t2 given this

2r * t2 = rx

t2-= x/ 2

Total time = X + X/2 = 3x/ 2
CEO
Joined: 29 Mar 2007
Posts: 2559

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17 Sep 2007, 21:10
ggarr wrote:
Mr. Jones drove from Town A to Town B in x hours. On the return trip over the same route, his average speed was twice as fast. Which of the following expresses the total number of driving hours for the round trip?

(A) 2x/3
(B) 3x/2
(C) 5x/3
(D) 2x
(E) 3x

traveled X hours from A to B.

Traveled X/2 hours from B to A.

X+X/2--> 2X/2+X/2=3X/2

B
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5043
Location: Singapore

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17 Sep 2007, 22:48
Let distance = D km/h

D = s(x) km

Let time taken for return trip be t

D = 2s(t) km

s(x) = 2s(t)
t = x/2 hours

total time = x + x/2 = 3x/2
17 Sep 2007, 22:48
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