Carcass 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 that 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) 4/3
(D) 8/5
(E) 3
There's 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
Answer: C
Cheers,
Brent