anilnandyala wrote:

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

A. 35

B. 40

C. 45

D. 50

E. 55

Average speed = (TOTAL distance)/(TOTAL time)TOTAL distanceSusan traveled 30 miles at a speed of 30mph, and 30 miles more at a speed of 60mph.

So, TOTAL distance = 30 miles + 30 miles =

60 miles TOTAL timeTOTAL time = (time spent driving 30 mph) + (time spent driving 60 mph)

time = distance/speed

- Time spent driving 30 mph = 30 miles/30mph =

1 hour

- Time spent driving 60 mph = 30 miles/60mph =

0.5 hours

TOTAL time = (

1 hour) + (

0.5 hours) =

1.5 hours----------------------------------

So, Average speed = (

TOTAL distance)/(

TOTAL time)

=

60 miles/

1.5 hours= 40 mph

Answer: B

Cheers,

Brent

_________________

Brent Hanneson – GMATPrepNow.com