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# Marla starts running around a circular track at the same

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Math Expert
Joined: 02 Sep 2009
Posts: 53020
Re: Marla starts running around a circular track at the same  [#permalink]

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11 Aug 2018, 12:41
Probus wrote:
Bunuel wrote:
enigma123 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

How to do this guys?

Marla completes 32-20=20 more laps in 1 hour. Marla to complete 4 (20/5=4) more laps will need 1/5 hours, which is 12 minutes.

Answer: C.

Hi Bunuel
Marla completes 32-12=20 , i guess its a typo error.

Probus

Yes. Edited. Thank you.
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Intern
Joined: 20 Mar 2018
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Marla starts running around a circular track at the same  [#permalink]

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08 Dec 2018, 15:59
Marla covers 32 laps per hour
Nick covers 12 laps per hour

Marla covers 20 more laps than Nick

Now, 20 laps is covered in ------------->60 mins
and, 1 lap is covered in ----------------->60/20 mins

Hence, 4 laps is covered in ---------> 4*60/20=3 mins
CEO
Joined: 11 Sep 2015
Posts: 3437
Location: Canada
Re: Marla starts running around a circular track at the same  [#permalink]

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29 Jan 2019, 09:58
Top Contributor
enigma123 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

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

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Joined: 30 Dec 2018
Posts: 4
Re: Marla starts running around a circular track at the same  [#permalink]

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01 Feb 2019, 10:01
Consider the length of the track to be 1 km:
now speed of Marla = 32km/hr and speed of Nick = 12km/hr
Question becomes after how many minutes the distance between the two becomes 4km/hr
take x = time in hours
--> 32x-12x=4
--> 20x=4
-->x=1/5=20 minutes
Re: Marla starts running around a circular track at the same   [#permalink] 01 Feb 2019, 10:01

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# Marla starts running around a circular track at the same

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