GreenlightTestPrep wrote:

On a road trip, Kip drove one-quarter the distance at an average speed of v miles per hour, one-quarter the distance at an average speed of 2v miles per hour, one-quarter the distance at 4v miles per hour, and one-quarter the distance at 8v miles per hour. In terms of v, what was Kip’s average speed (in miles per hour) for the entire trip?

A) 15/4v

B) 15v/4

C) 32v/15

D) 4v/15

E) 15v/32

Since we aren't told the total distance, let's

assign a nice value to the distance.

Let's say

32 miles = TOTAL distance.

So, each quarter =

8 miles

Average speed = total distance/total travel timeSo, we must find the travel time for EACH QUARTER and add them together.

Time = distance/speed, so:

Time spent driving v mph =

8/v = 8/v

Time spent driving 2v mph =

8/2v = 4/v

Time spent driving 4v mph =

8/4v = 2/v

Time spent driving 8v mph =

8/8v = 1/v

TOTAL travel time = 8/v + 4/v + 2/v + 1/v

=

15/v Average speed = total distance/total travel time=

32/(

15/v)

= (

32)(

v/15)

= 32v/15

Answer: C

Cheers,

Brent

_________________

Brent Hanneson – Creator of greenlighttestprep.com

Sign up for our free GRE Question of the Day emails