During a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60 miles per hour. His travel time for the xmile trip was what percent greater than it would have been if he had traveled at a constant rate of 60 miles per hour for the entire trip?
A. 8.5%
B. 50%
C. x/12%
D. 60/x%
E. 500/x%
OA E
Source: GMAT Prep
During a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5mile section of the expre
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Don drove a total of x miles. His average speed on a certain 5mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60 miles per hour.BTGmoderatorDC wrote: ↑Fri Sep 23, 2022 4:50 pmDuring a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60 miles per hour. His travel time for the xmile trip was what percent greater than it would have been if he had traveled at a constant rate of 60 miles per hour for the entire trip?
A. 8.5%
B. 50%
C. x/12%
D. 60/x%
E. 500/x%
OA E
Source: GMAT Prep
Total time = (time spent driving 30 mph) + (time spent driving 60 mph)
time = distance/speed
So, total driving time = 5/30 + (x  5)/60
= 10/60 + (x  5)/60
= (10 + x  5)/60
= (x + 5)/60
Hypothetically speaking, Don could have driven the entire x miles at a speed of 60 mph
time = distance/speed
Total driving time = x/60
His travel time for the xmile trip was what percent greater than it would have been if he had traveled at a constant rate of 60 miles per hour for the entire trip?
In other word: (x + 5)/60 is what percent greater than x/60?
Percentage = 100[(x + 5)/60  x/60]/(x/60)
= 100[5/60]/(x/60)
= 100(5/60)(60/x)
= 500/x
Answer: E
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We are given that Don drove a total of x miles, his average speed on a 5mile section of the expressway was 30 mph, and his average speed for the remainder of the trip, or x  5 miles, was 60 mph.BTGmoderatorDC wrote: ↑Fri Sep 23, 2022 4:50 pmDuring a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60 miles per hour. His travel time for the xmile trip was what percent greater than it would have been if he had traveled at a constant rate of 60 miles per hour for the entire trip?
A. 8.5%
B. 50%
C. x/12%
D. 60/x%
E. 500/x%
OA E
Source: GMAT Prep
Since time = distance/rate, the time for the first 5mile section was 5/30 = 1/6 of an hour, and the time for the remainder of the trip was (x5)/60 hours.
Thus, the total time was 1/6 + (x5)/60 = 10/60 + (x5)/60 = (x + 5)/60 hours.
Had he traveled at a constant rate of 60 miles per hour for the entire trip, then his time would have been x/60 hours.
We need to determine the percent by which (x + 5)/60 is greater than x/60. We use the percent change formula: (New  Old)/Old * 100%.
[(x + 5)/60  x/60]/(x/60) * 100%
(5/60)/(x/60) * 100%
5/x * 100%
500/x%
Answer: E
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