varun289 wrote:During a trip, Francine traveled x percent of the total distance at an average speed of 40 miles per hour and the rest of the distance at an average speed of 60 miles per hour. In terms of x, what was Francine's average speed for the entire trip?
A. (1800 - x) /2
B. (x + 60) /2
C. (300 - x ) / 5
D. 600 / (115 - x )
E. 12,000 / ( x + 200)
Let x=50, so that 50% of the distance is traveled at 40mph and 50% is traveled at 60mph.
When the same distance is traveled at two different speeds, the average speed for the entire trip will be just a bit LESS than the average of the two speeds.
Since (40+60)/2 = 50, the average speed for Francine's entire trip must be just a bit less than 50.
Now plug x=50 into the answers to see which yields an average speed just a bit less than 50.
Only
E works:
12,000/(x+200) = 12,000/(50+200) = 48.
The correct answer is
E.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
