If Lucy walks to work at a rate of 4 miles per hour, but she

Source: Manhattan Prep

If Lucy walks to work at a rate of 4 miles per hour, but she walks home by the same route at a rate of 6 miles per hour, what is Lucy's average walking rate for the round trip?

A. 4.2 miles/hour
B. 4.4 miles/hour
C. 4.8 miles/hour
D. 5 miles/hour
E. 5.8 miles/hour

The OA is C

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pm; Location: Vancouver, BC; Thanked: 5254 times; Followed by:1268 members; GMAT Score:770

by Brent@GMATPrepNow » Wed Jun 26, 2019 4:12 am

BTGmoderatorLU wrote:Source: Manhattan Prep

If Lucy walks to work at a rate of 4 miles per hour, but she walks home by the same route at a rate of 6 miles per hour, what is Lucy's average walking rate for the round trip?

A. 4.2 miles/hour
B. 4.4 miles/hour
C. 4.8 miles/hour
D. 5 miles/hour
E. 5.8 miles/hour

The OA is C

Let d = distance from home to work

Average speed = (total distance traveled)/(total travel time)

total distance traveled = d + d = 2d

total travel time = travel time TO work + travel time FROM work

time = distance/speed

We get: total travel time = d/4 + d/6
= 3d/12 + 2d/12
= 5d/12

Average speed = 2d/(5d/12)
= (2d)(12/5d)
= 24d/5d
= 24/5
= 4.8

Answer: C

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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Scott@TargetTestPrep: GMAT Instructor; Posts: 7261; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Mon Jul 01, 2019 4:09 pm

BTGmoderatorLU wrote:Source: Manhattan Prep

If Lucy walks to work at a rate of 4 miles per hour, but she walks home by the same route at a rate of 6 miles per hour, what is Lucy's average walking rate for the round trip?

A. 4.2 miles/hour
B. 4.4 miles/hour
C. 4.8 miles/hour
D. 5 miles/hour
E. 5.8 miles/hour

The OA is C

We can use the equation:

average speed = (total distance)/(total time)

If we let distance each way = 12, we have:

Average = (12 + 12)/(12/4 + 12/6)

Average = 24/5 = 4.8 mph

Answer: C

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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