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On a track for remote controlled racing cars

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Joined: 08 Oct 2016
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On a track for remote controlled racing cars [#permalink]

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New post 14 Nov 2016, 06:34
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Difficulty:

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Question Stats:

68% (01:28) correct 32% (02:10) wrong based on 197 sessions

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On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these
[Reveal] Spoiler: OA

Kudos [?]: 24 [0], given: 11

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Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3106

Kudos [?]: 1145 [0], given: 327

Location: India
GPA: 3.5
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Re: On a track for remote controlled racing cars [#permalink]

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New post 14 Nov 2016, 10:14
voccubd wrote:
On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these


Time required in seconds will be LCM ( 35, 55 ) = 385

Hence, answer will be (C) 385

_________________

Thanks and Regards

Abhishek....

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Kudos [?]: 1145 [0], given: 327

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Re: On a track for remote controlled racing cars [#permalink]

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New post 14 Nov 2016, 11:02
Abhishek009 wrote:
voccubd wrote:
On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these


Time required in seconds will be LCM ( 35, 55 ) = 385

Hence, answer will be (C) 385


Sorry I can't understand. Can you please explain in details or suggest me any resource material on this ? I found another similar problem in the internet where L.C.M wasn't the answer.

Kudos [?]: 24 [0], given: 11

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Status: QA & VA Forum Moderator
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Re: On a track for remote controlled racing cars [#permalink]

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New post 14 Nov 2016, 11:11
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voccubd wrote:
Abhishek009 wrote:
voccubd wrote:
On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these


Time required in seconds will be LCM ( 35, 55 ) = 385

Hence, answer will be (C) 385


Sorry I can't understand. Can you please explain in details or suggest me any resource material on this ? I found another similar problem in the internet where L.C.M wasn't the answer.


Cumulative lap timings of Car A and Car B is as follows -

Car A = { 55 , 110 , 165 , 220 , 275 , 330 , 385 , 440..........}

Car B = { 35, 70, 105 , 140 , 175 , 210 , 245 , 280 , 315 , 350 , 385, 420........}


Since, both are independent events, they will start again at 385 seconds ( from starting ) , hence, LCM is preferred here..
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

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Joined: 07 Dec 2014
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Re: On a track for remote controlled racing cars [#permalink]

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New post 14 Nov 2016, 19:06
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voccubd wrote:
On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these


55=11*5
35=7*5
lcm=11*7*5=385

Kudos [?]: 291 [1], given: 16

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Re: On a track for remote controlled racing cars [#permalink]

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New post 28 Nov 2016, 04:10
gracie wrote:
voccubd wrote:
On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these


55=11*5
35=7*5
lcm=11*7*5=385


Bunuel/Experts

What will be the approach if question mentions that Car b started 10 minuter after Car A??

THanks
Rohit

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Joined: 30 May 2012
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Location: United States (TX)
Concentration: Finance, Marketing
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On a track for remote controlled racing cars [#permalink]

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New post 26 Sep 2017, 16:38
rohit8865 wrote:
gracie wrote:
voccubd wrote:
On a track for remote controlled racing cars, racing car A completes the track in 55 seconds, while racing car B completes it in 35 seconds. If they both start at the same time after how many seconds will they be side by side again.

A. 275
B. 325
C. 385
D. 425
E. None of these


55=11*5
35=7*5
lcm=11*7*5=385


Bunuel/Experts

What will be the approach if question mentions that Car b started 10 minuter after Car A??

THanks
Rohit



rohit8865 - I am no expert but here is my dig on it.

Speed of Car A = 1/35
Speed of Car B = 1/55

Convert 10 minutes to seconds. That will be 600 secs

Distance traveled by Car A in 600 secs = 600/55 = 120/11 laps.

Relative speed = \(\frac{1}{35}-\frac{1}{55}\) [subtract slower from faster because they are traveling in the same direction]
So, Relative speed = \(\frac{4}{385}\)

Relative distance = 120/11 laps.

Time when they meet = \(\frac{\frac{120}{11}}{\frac{4}{385}}\) = 1050 secs or 17.5 mins.

Hope I am correct :)

Kudos [?]: 84 [0], given: 151

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Joined: 24 Jun 2017
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Re: On a track for remote controlled racing cars [#permalink]

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New post 26 Sep 2017, 18:41
55x=35y (point in time when they run side by side)
x=35y/55 (integer, seconds)

x= 7*5*y/5*11, then y = 11, so 385
you can read it as in 385 secs car A(x) will 7 complete tracks and car B 11

Kudos [?]: 14 [0], given: 129

Re: On a track for remote controlled racing cars   [#permalink] 26 Sep 2017, 18:41
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