Swimming Race Rate Problem

Oldest

Best Reply

Author

Message

TAGS:

Status: The last round

Joined: 18 Jun 2009

Posts: 1325

Concentration: Strategy, General Management

Schools: Stanford '14 (D), Booth '14 (D), Johnson '14 (D)

GMAT 1: 680 Q48 V34

Followers: 44

Kudos [?]: 386 [1] , given: 156

Swimming Race Rate Problem [#permalink]

13 Mar 2010, 11:11

This post received
KUDOS

00:00

Question Stats:

0% (00:00) correct

0% (00:00) wrong

based on 0 sessions

Hardy and Andy start a two-length swimming race at the same moment but from opposite ends of the pool. They swim in lanes at uniform speeds, but Hardy is faster than Andy. They 1st pass at a point 18.5m from the deep end and having completed one length each 1 is allowed to rest on the edge for exactly 45 sec. After setting off on the return length, the swimmers pass for the 2nd time just 10.5m from the shallow end. How long is the pool?

A. 55.5 m
B. 45 m
C. 66 m
D. 49 m
E. 54 m
_________________

[ From 470 to 680-My Story ] [ My Last Month Before Test ]
[ GMAT Prep Analysis Tool ] [ US. Business School Dashboard ] [ Int. Business School Dashboard ]

I Can, I Will

Find out what's new at GMAT Club - latest features and updates

Senior Manager

Joined: 13 Dec 2009

Posts: 268

Followers: 8

Kudos [?]: 70 [0], given: 13

Re: Swimming Race Rate Problem [#permalink]

13 Mar 2010, 11:42

Really tough question!!. Couldn't solve it yet..
_________________

My debrief: done-and-dusted-730-q49-v40

Senior Manager

Joined: 01 Feb 2010

Posts: 275

Followers: 1

Kudos [?]: 30 [0], given: 2

Re: Swimming Race Rate Problem [#permalink]

13 Mar 2010, 22:47

Hussain15 wrote:

Whats the source of problem?

Status: The last round

Joined: 18 Jun 2009

Posts: 1325

Concentration: Strategy, General Management

Schools: Stanford '14 (D), Booth '14 (D), Johnson '14 (D)

GMAT 1: 680 Q48 V34

Followers: 44

Kudos [?]: 386 [0], given: 156

Re: Swimming Race Rate Problem [#permalink]

14 Mar 2010, 22:22

I got this question from the past thread of this forum.

Kindly answer the question with explanation.
_________________

Senior Manager

Joined: 30 Aug 2009

Posts: 295

Location: India

Concentration: General Management

Followers: 2

Kudos [?]: 65 [0], given: 5

Re: Swimming Race Rate Problem [#permalink]

15 Mar 2010, 08:12

Let Length of Pool be L, speed of Hardy be H and that of Andy be A. Given H>A

They 1st pass at a point 18.5m from the deep end

(L - 18.5)/H = 18.5/A --- eqn1

1/A = (L - 18.5)/18.5 H ------eqn2

They cross for 2nd time at a point 10.5m from the shallow end

(L - 10.5)/ H = 10.5/A ----eqn3

now total time spent by both from 1st end to 2nd end ,plus wait period and crossing for second time will be equal i.e.

L/H + 45 + (L - 10.5)/ H = L/A +45 + 10.5/A

on solving this we get
(2L - 10.5)/H = (L+10.5)/A----eqn 4

substituting the value of 1/A from eqn2 in eqn 4 we get

(2L - 10.5)/H = (L+10.5) * (L - 18.5)/18.5 H, on solving this we get L = 45

Senior Manager

Joined: 13 Dec 2009

Posts: 268

Followers: 8

Kudos [?]: 70 [0], given: 13

Re: Swimming Race Rate Problem [#permalink]

15 Mar 2010, 08:21

kp1811 wrote:

(L - 18.5)/H = 18.5/A --- eqn1

Awesome solution man...just one question. How can you say that Hardy started from the shallow end?
_________________

My debrief: done-and-dusted-730-q49-v40

Senior Manager

Joined: 30 Aug 2009

Posts: 295

Location: India

Concentration: General Management

Followers: 2

Kudos [?]: 65 [0], given: 5

Re: Swimming Race Rate Problem [#permalink]

15 Mar 2010, 09:07

sidhu4u wrote:

kp1811 wrote:

(L - 18.5)/H = 18.5/A --- eqn1

Awesome solution man...just one question. How can you say that Hardy started from the shallow end?

even if we consider the opposite it doesn't affect the final answer as we substitute for A or H and H or A cancels out.

Moreover from answer options we know the midpoint is 22.5 (considering the lowest value of 45 among the answer choices) and since H>A we can intuitively assume that Hardy started from shallow end.

solving it the other way i.e. Hardy is at Deep end initially
Let Length of Pool be L, speed of Hardy be H and that of Andy be A. Given H>A

They 1st pass at a point 18.5m from the deep end

(L - 18.5)/A = 18.5/H --- eqn1

1/A = 18.5/(L - 18.5) H ------eqn2

They cross for 2nd time at a point 10.5m from the shallow end

(L - 10.5)/ A = 10.5/H ----eqn3

now total time spent by both from 1st end to 2nd end ,plus wait period and crossing for second time will be equal i.e.

L/A + 45 + (L - 10.5)/ A = L/H +45 + 10.5/H

on solving this we get
(2L - 10.5)/A = (L+10.5)/H----eqn 4

substituting the value of 1/A from eqn2 in eqn 4 we get

(L + 10.5)/H = (2L -10.5) * 18.5/(L - 18.5) H, on solving this still we get L = 45

Senior Manager

Joined: 13 Dec 2009

Posts: 268

Followers: 8

Kudos [?]: 70 [0], given: 13

Re: Swimming Race Rate Problem [#permalink]

15 Mar 2010, 11:50

Thanks...understood now
_________________

My debrief: done-and-dusted-730-q49-v40

Re: Swimming Race Rate Problem [#permalink] 15 Mar 2010, 11:50

		Similar topics	Author	Replies	Last post
Similar Topics:		RACES PROBLEMS	mand-y	0	12 Jul 2006, 03:04
		ds racing problem	mand-y	3	12 Jul 2006, 15:59
	2	swimming!!!!	Abhishek.pitti	15	18 Jan 2009, 19:30
	2	Jim takes a seconds to swim c meters at a constant rate	aditi2013	9	07 Dec 2012, 20:12
	4	Jim takes a seconds to swim c meters at a constant rate from	samsikka23	6	08 Jan 2013, 04:14

Swimming Race Rate Problem

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

Swimming Race Rate Problem

Swimming Race Rate Problem

Main navigation

GMAT Resources

Partners

MBA Resources