David drove to work at an average (arithmetic mean) speed of 45

[BTGModeratorVI]

David drove to work at an average (arithmetic mean) speed of 45 miles per hour. After work, David drove home at an average speed of 60 miles per hour. If David spent a total of 2 hours commuting to and from work, how many miles does David drive to work?

A. 48
B. 256/5
C. 360/7
D. 105/2
E. 160/3

Answer: C
Source: Magoosh

[Brent@GMATPrepNow]

David drove to work at an average (arithmetic mean) speed of 45 miles per hour. After work, David drove home at an average speed of 60 miles per hour. If David spent a total of 2 hours commuting to and from work, how many miles does David drive to work?

A. 48
B. 256/5
C. 360/7
D. 105/2
E. 160/3

Answer: C
Source: Magoosh

Let's start with a "word equation"
We can write: (David's travel time TO work) + (David's travel time FROM work) = 2 hours
time = distance/speed

Let d = the distance each way

We can write: d/45 + d/60 = 2
To eliminate the fractions, multiply both sides by 180, the LCM of 45 and 60

We get: 4d + 3d = 360
Simplify: 7d = 360
Solve: d = 360/7

Answer: C

Cheers,
Brent