While on a straight road, car X & car Y are travelling at different constant rates. If car X is now 1 mile ahead of car Y, how many minutes from now will car X be 2 miles ahead of car Y?
1) Car X is travelling at 50 miles per hour and car Y is travelling at 40 miles per hour.
2) Three minutes ago car X was 1/2 miles ahead of car Y
Pls explain in detail
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romitvsingh
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(1) As the cars are moving in the same direction, relative speed of the cars = (50 - 40) = 10 miles per hour.romitvsingh wrote:While on a straight road, car X & car Y are travelling at different constant rates. If car X is now 1 mile ahead of car Y, how many minutes from now will car X be 2 miles ahead of car Y?
1) Car X is travelling at 50 miles per hour and car Y is travelling at 40 miles per hour.
2) Three minutes ago car X was 1/2 miles ahead of car Y
Pls explain in detail
Total distance between them cover = (2 - 1) = 1 mile
Hence, time required = 1/10 hour = 6 minutes; SUFFICIENT.
(2) In three minutes, car X is (1 - 1/2) = 1/2 miles ahead of car Y.
Hence, relative speed of the cars = 1/2 miles per 3 minute = 1 mile per 6 minute
Total distance between them cover = (2 - 1) = 1 mile
Hence, time required = 6 minutes; SUFFICIENT.
The correct answer is D.
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chufus
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A.
Car X travels 50/60 = 5/6 miles per minute
Car Y travels 40/60 = 4/6 miles per minute
Distance travelled by X = x
Distance travelled by Y = x-1
Time taken by both is the same.
Time is distance/speed
so x/(5/6) = x-1/(4/6)
Solve to find x = 5 miles
Distance is 5 miles, speed is 5/6 miles per minute
So > 5(5/6) = 6 minutes
SUFFICIENT
B. 3 minutes ago they were 1/2 miles apart and now they are 1 mile apart. So X gains half a mile every 3 minutes since they are at constant speed.
Hence to add a mile would take 3*2 = 6 Minutes
SUFFICIENT
Pick "D"[/b]
Car X travels 50/60 = 5/6 miles per minute
Car Y travels 40/60 = 4/6 miles per minute
Distance travelled by X = x
Distance travelled by Y = x-1
Time taken by both is the same.
Time is distance/speed
so x/(5/6) = x-1/(4/6)
Solve to find x = 5 miles
Distance is 5 miles, speed is 5/6 miles per minute
So > 5(5/6) = 6 minutes
SUFFICIENT
B. 3 minutes ago they were 1/2 miles apart and now they are 1 mile apart. So X gains half a mile every 3 minutes since they are at constant speed.
Hence to add a mile would take 3*2 = 6 Minutes
SUFFICIENT
Pick "D"[/b]
