John and Mike

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Scaramanga: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Sun Mar 15, 2009 2:42 am; Thanked: 1 times

by Scaramanga » Wed Mar 18, 2009 3:52 am

John and Mike drove separate cars along the entire length of a certain route. If John made the trip in 15 minutes, how many minutes did it take Mike to make the same trip?

(1) Mike’s average speed for the trip was 3/4 of John’s average speed.

(2) The route is 14 miles long.

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Source: Beat The GMAT — Data Sufficiency | Wed Mar 18, 2009 3:52 am

kanak_p: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Mar 19, 2009 3:44 am

by kanak_p » Thu Mar 19, 2009 4:06 am

Based on first principle Distance = Speed x Time; If we write the eqn for John and Mike separately
Distance (John) = Speed (J) x Time (J) ..... 1
Distance (Mike) = Speed (M) x Time (M) ..... 2

Since the total distance traveled is same i.e Distance (J) = Distance (M)
From eqn 1 and 2 above
Speed (J) x Time (J) = Speed (M) x Time (M)
Time (M) = Speed (J) X Time (J)/Speed (M)

Per statement I Speed(M)/Speed(J) = 3/4
Time (M) = (4/3) * 15 =20min5 * 15/3 = 20min
Statement I is enough.

Based on Statement II we can only arrive at speed of John and no more information is available either on relative time of arrival or relative speed and hence II is not enough.

I would go with option A, statement I alone is enough. BTW, what is OA?

Kanak

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kapitalist: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Tue Oct 21, 2008 10:37 pm

by kapitalist » Fri Mar 20, 2009 12:08 am

but it says AVERAGE speed...which doesnt really tell you anything,

I would say E if its any recollection of the questions I've had where they try to trick you by saying Average speed.

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Vemuri: Legendary Member; Posts: 682; Joined: Fri Jan 16, 2009 2:40 amFollowed by: 1 member; Thanked: 32 times

Re: John and Mike

by Vemuri » Fri Mar 20, 2009 1:17 am

Don't think that all average speed questions are tricky & answer choices that have that wording are wrong. In this case average speed should be good enough information. We are dealing with the entire length for both the people. So, as per the formula:

Avg speed = (Total Distance)/(Total time taken)

Stmt 2 just gives the distance, we don't know anything about their individual speeds, so not good enough.

A is sufficient to answer the question.

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kapitalist: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Tue Oct 21, 2008 10:37 pm

by kapitalist » Mon Mar 23, 2009 12:27 am

so what IS the correct answer???????

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rs2010: Master | Next Rank: 500 Posts; Posts: 232; Joined: Fri Jul 04, 2008 4:14 pmFollowed by: 1 member; Thanked: 14 times; GMAT Score:760

by rs2010 » Mon Mar 23, 2009 7:55 am

kapitalist wrote:so what IS the correct answer???????

If it comes out other than A then dont rely on the source.

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