percentages + distance

[Woozler]

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 mph, and his average speed for the remainder of the trip was 60 mph. 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 mph for the entire trip?

A 8.5%
B 50%
C x/12 %
D 60/x %
E 500/x %

This can be solved by plugging and chugging, but I cannot figure out the algebraic solution to this.

[towerSpider]

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 mph, and his average speed for the remainder of the trip was 60 mph. 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 mph for the entire trip?

A 8.5%
B 50%
C x/12 %
D 60/x %
E 500/x %

This can be solved by plugging and chugging, but I cannot figure out the algebraic solution to this.

entire at 60 mph: x/60
entire otherwise: 5/30+(x-5)/60, 1/6+(x-5)/60, (10+(x-5))/60, (10+x-5)/60, (5+x)/60

(5+x)/60 - x/60
5/60
1/12

1/12 / x/60 * 100
1/12 * 60/x * 100

6000/12x
500/x%

E is answer.

[Woozler]

I cannot even do basic algebra, yet I still scored 49 (initially) on GMAT prep 2. Do other people even study?

Thank you very much.

[frank1]

I cannot even do basic algebra, yet I still scored 49 (initially) on GMAT prep 2. Do other people even study?

Thank you very much.

and that is one thing i dont understand....
and i can do most of the things and have taken more than thousand of question from different sources and still the prep test score doesnt go higher than 46-47....

i really dont understand the thing....
many people are saying they are scoring more than 700 with out much hussle....

dont know whats wrong.....

[diebeatsthegmat]

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 mph, and his average speed for the remainder of the trip was 60 mph. 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 mph for the entire trip?

A 8.5%
B 50%
C x/12 %
D 60/x %
E 500/x %

This can be solved by plugging and chugging, but I cannot figure out the algebraic solution to this.

you just solve it as normal.

D1=5 so D2=x-5
t1=5/30=10/60
t2=(x-5)/60
T=t1+t2=(x+5)/60 and the total time for the whole trip it takes for 60 kmh is x/60
so the percent of time is (x/60+5/60 -x/60)/x/60=5/60*60/x*100%=E