Problem Solving

Maura drives to work in 40 minutes. She takes the same route to return home. If her average speed on trip home is half as fast as her average speed on the trip to work, how much time does she spend driving on the round trip?

A-1hr
B-1hr 15 mins
C-1 hr 20 mins
D-1 hr 40 mins
E- 2 hrs

Home to work
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t=40 mins

speed=x

D=40x

Work to home
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distance from work to home is same as home to work

D=40x

s=x/2

t=40x/x/2=80

total time =40+80=120=2hrs

bpgen wrote:Maura drives to work in 40 minutes. She takes the same route to return home. If her average speed on trip home is half as fast as her average speed on the trip to work, how much time does she spend driving on the round trip?

A-1hr
B-1hr 15 mins
C-1 hr 20 mins
D-1 hr 40 mins
E- 2 hrs

The algebraic solution provided is correct; we can also reason it out.

Given a fixed distance, time and speed are inversely proportional.

On this question, her speed home is half as fast as her speed to work; if you cut your speed in half, you must double your time to cover the same distance.

So, her time home is 2*40 minutes = 80 minutes.

40 + 80 = 120 minutes = 2 hours... choose (E).