swerve wrote:Marla starts running around a circular track at the same time Nick starts walking around the same circular track. Marla completes 32 laps around the track per hour and Nick completes 12 laps around the track per hour. How many minutes after Marla and Nick begin moving will Marla have completed 4 more laps around the track than Nick?

A. 5
B. 8
C. 12
D. 15
E. 20

The OA is C

Source: GMAT Prep

With the given information, Marla completes 32 - 12 = 20 more laps in one hour than Nick

Thus, she completes 4 more laps than Nick in (1/20)*4 = 1/5 hours = 60/5 = 12 minutes

The correct answer: C

Hope this helps!

-Jay
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swerve wrote:Marla starts running around a circular track at the same time Nick starts walking around the same circular track. Marla completes 32 laps around the track per hour and Nick completes 12 laps around the track per hour. How many minutes after Marla and Nick begin moving will Marla have completed 4 more laps around the track than Nick?

A. 5
B. 8
C. 12
D. 15
E. 20

The OA is C

Source: GMAT Prep

We can use the following formula:

time = change in distance/change in rate

time = 4/20 = 1/5 hour = 12 minutes

Alternate Solution:

Note that Marla's rate is 32/60 laps per minute and Nick's rate is 12/60 laps per minute. Let's say after t minutes, Marla completes 4 more laps than Nick. Then, in t minutes Marla completes 32t/60 laps and Nick completes 12t/60 laps. Since the number of laps completed by Marla is 4 more than the number completed by Nick, we have:

32t/60 = 12t/60 + 4

32t/60 - 12t/60 = 4

20t/60 = 4

t/3 = 4

t = 12

Alternate Solution:

We see that in 1 hour, or 60 minutes, Marla has completed 20 laps more than Nick. We can set up a proportion, letting x = the number of minutes it takes for Marla to complete 4 more laps than Nick.

60/20 = x/4

3 = x/4

12 = x

Thus, it takes 12 minutes for Marla to complete 4 more laps than Nick.

Answer: C

swerve wrote: ↑

Thu Jan 02, 2020 10:07 am

Marla starts running around a circular track at the same time Nick starts walking around the same circular track. Marla completes 32 laps around the track per hour and Nick completes 12 laps around the track per hour. How many minutes after Marla and Nick begin moving will Marla have completed 4 more laps around the track than Nick?

A. 5
B. 8
C. 12
D. 15
E. 20

The OA is C

Source: GMAT Prep

Let t = the time (in HOURS) that it takes Marla to complete 4 more laps than Nick.
So, after t hours, we can write: (Marla's lap count) = (Nick's lap count) + 4

Now that we have a "word equation" we need only fill in the missing information

Marla completes 32 laps per hour
We can think of 1 lap as being a unit of distance.
So, 32 laps per hour is Marla's speed.

Distance = (speed)(time)
So, after t hours, Marla's lap count = 32t


Nick completes 12 laps around the track per hour
So, after t hours, Nick's lap count = 12t

We can now plug the above values into the word equation.
We get: 32t = 12t + 4
Subtract 12t from both sides to get: 20t = 4
Solve: t = 4/20 = 1/5 HOURS

1/5 hours = 12 minutes.

Answer: C