mangamma wrote:
Car M was driving on a highway at a constant speed of 50 miles per hour. If Car N was 3 miles behind Car M 20 minutes ago and 2 miles ahead of Car M 5 minutes ago, what was the speed of Car N? Assume that Car N was driving at a constant speed.
A. 60 miles per hour
B. 70 miles per hour
C. 90 miles per hour
D. 100 miles per hour
E. 110 miles per hour
Car M travels at 50mph, and car N covers (3+2)miles in (20-5) minutes over car M. So it travels 5 miles more in 15 minutes or 5*4 in 15*4 min, that is 20 miles in an hour.
Thus the speed of car N is 50+20 or 70 mph.
B
_________________
1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html
4) Base while finding % increase and % decrease : https://gmatclub.com/forum/percentage-increase-decrease-what-should-be-the-denominator-287528.html
GMAT Expert