Speed Problem!

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Ozlemg: Master | Next Rank: 500 Posts; Posts: 407; Joined: Tue Jan 25, 2011 9:19 am; Thanked: 25 times; Followed by:7 members

Speed Problem!

by Ozlemg » Fri Jul 15, 2011 4:41 am

Car X and Car Y traveled the same 80-mile route. If Car X took 2 hours and Car Y traveled at an average speed the was 50 percent faster than the average speed of Car X, how many hours did it take Car Y to travel the route?

(A) 2/3 (B) 1 (C) 1 1/3 (D) 1 3/5 (E) 3

OA will follow...
PS : There is a one clever short-cut!

Last edited by Ozlemg on Fri Jul 15, 2011 5:02 am, edited 1 time in total.

The more you suffer before the test, the less you will do so in the test!

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Source: Beat The GMAT — Problem Solving | Fri Jul 15, 2011 4:41 am

vineeshp: Legendary Member; Posts: 965; Joined: Thu Jan 28, 2010 12:52 am; Thanked: 156 times; Followed by:34 members; GMAT Score:720

by vineeshp » Fri Jul 15, 2011 4:49 am

Car X took 2 hours to complete 80 miles. That means his speed is 80 / 2 = 40 miles per hour.

Speed of Y is 50% more than X. which means his speed is 40 + 50% of 40 = 60.

So time taken = 80/60 = 4/3 = 1 1/3.

Vineesh,
Just telling you what I know and think. I am not the expert.

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GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pm; Location: Vancouver, BC; Thanked: 5254 times; Followed by:1268 members; GMAT Score:770

by Brent@GMATPrepNow » Fri Jul 15, 2011 5:28 am

Ozlemg wrote:Car X and Car Y traveled the same 80-mile route. If Car X took 2 hours and Car Y traveled at an average speed the was 50 percent faster than the average speed of Car X, how many hours did it take Car Y to travel the route?

(A) 2/3 (B) 1 (C) 1 1/3 (D) 1 3/5 (E) 3

There's also a nice rule we can use here.
To set up the rule, recognize that if Y travels 2 times as fast as X, then Y's travel time will be 1/2 of X's.
Similarly, if Y travels 3 times as fast as X, then Y's travel time will be 1/3 of X's.
Or if Y travels 1/4 as fast as X, then Y's travel time will be 4 times X's travel time.

In general, if Y travels a/b times as fast as X, then Y's travel time will be b/a of X's travel time.

So, if Y's speed is 50% more than X's speed, we can say that Y travels 1.5 times as fast as X.
In other words, if Y travels 3/2 times as fast as X, which means Y's travel time will be 2/3 that of X's travel time.

Since X's travel time is 2 hours, Y's travel time will be (2/3)(2) = 4/3 = 1 1/3 = C

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Fri Dec 15, 2017 6:35 am

Ozlemg wrote:Car X and Car Y traveled the same 80-mile route. If Car X took 2 hours and Car Y traveled at an average speed the was 50 percent faster than the average speed of Car X, how many hours did it take Car Y to travel the route?

(A) 2/3 (B) 1 (C) 1 1/3 (D) 1 3/5 (E) 3

We are given that Car X traveled 80 miles in 2 hours. Thus, the rate of car X was 80/2 = 40 mph.

We are also given that Car Y traveled 50% faster than Car X. Thus, Car Y traveled at a rate of 1.5 x 40 = 60 mph.

So, it took Car Y 80/60 = 8/6 = 4/3 hours to travel the route.

Answer: C

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