ludwigvb wrote:

During a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5-mile 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 x-mile 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%

average speed on the 5 mile section =30 miles per hour =5/t1

t1=5/30 =1/6 hour

where t1 is the time taken by Don to cover the 5 mile section

let t2 be the time taken by don to cover the remaining

then ,

t2=x-5/60

total time taken t=t1+t2=1/6+(x-5)/60=(x+5)/60

additional time taken =5/60=1/12

If Don had driven at 60 miles per hour t3=x/60

His travel time for the x-mile trip was what percent greater than it would have been if he had travelled at a constant rate of 60 miles per hour for the entire trip?

ratio = (1/12)*100/(x/60)=(500/x)%