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gmat prep average speed

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gmat prep average speed

by wawatan » Sat May 17, 2008 9:28 pm
a truck and a station wagon are traveling at different constant rates on a straight road. If the truck is now 2 miles ahead of the station wagon, how many minutes from now will the truck be 5 miles ahead?

1) The truck is traveling at 70 mph, and the station wagon is traveling at 65 mph

2) 1 hour ago the truck was 3 miles behind the station wagon.

OA is D.

please help. i don't understand how both statements are sufficient. i thought answer was C.
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Source: — Data Sufficiency |
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by luvaduva » Sat May 17, 2008 10:57 pm
Important items from the stem: 2, 5, and minutes

(1) Think of the SW as not moving and the truck is 2 miles ahead of it. Subtract the SW speed from the truck's speed..70-65 = 5. So, think of the truck as going 5 mph. How long will it take the truck to go 3 miles?

d = rt => 3 = 5t => t = 3/5 hours => 3/5 hours*60min = 42 minutes

(2) In 1 hour the truck has gone 5 miles. How long will it take for it to go three miles? Set up a ratio and cross multiply: 1/5 = x/3 => x = 3/5 hour *60 = 42 minutes
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by wawatan » Sun May 18, 2008 12:43 am
thanks so much! that makes alot of sense
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