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Jack and Jill are marathon runners. Jack can finish a marathon (42 km)

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Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 08 Dec 2015, 03:12
2
5
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

77% (01:41) correct 23% (01:52) wrong based on 300 sessions

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Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post Updated on: 08 Dec 2015, 05:07
1
speed is inversely proportional to time
or
s1/s2=t2/t1
t1/t2=4.5/4.2=s2/s1
therefore.
Jack/jill=14/15

Originally posted by CounterSniper on 08 Dec 2015, 03:28.
Last edited by CounterSniper on 08 Dec 2015, 05:07, edited 2 times in total.
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 08 Dec 2015, 04:24
1
Average Speed of Jack =Distance/ Time
= 42 /(9/2) = 84/9

Average Speed of Jill = 42/(4.2) = 10

Ratio of Average speed of Jack to Jill = (84/9)/10 = 84/90 = 14/15

Answer A
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 08 Dec 2015, 04:48
jack speed =42/4.5

jill speed = 42/4.2

jack speed : jill speed 4.2 :4.5 =14/15
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 09 Apr 2016, 14:26
distance being the same for both the runners jack and jill. Ratio of speeds of jack to jill's speed will be inverse of ratio of time required by them to complete the marathon
(Jill's Time/Jack's Time) - 4.2/4.5 = 14/15
Correct answer - A
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 24 Jun 2017, 08:14
1
1
\(R= \frac{D}{T}\)
Rate of Jack = \(\frac{42}{4.5}\) and Rate of Jill = \(\frac{42}{4.2}\)

\(\frac{Jack}{Jill}=\frac{420}{45} * \frac{42}{420}\) = \(\frac{42}{45} = \frac{14}{15}\)

Answer is A
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 02 Apr 2019, 09:09
Bunuel

Should the answer be not E ? Because we do not know the length of the marathon of the Jill. If by any chance we are assuming that both the marathon distances are same then I guess there need some necessary changes in the question.
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)  [#permalink]

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New post 04 Apr 2019, 18:51
Bunuel wrote:
Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 4.5 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)

A. 14/15
B. 15/14
C. 4/5
D. 5/4
E. Cannot be determined


Jacks’ average speed is 42 km/4.5 hours, and Jill’s average speed is 42 km/4.2 hours. Thus, the ratio of their average speeds (Jack : Jill) is:

(42/4.5)/(42/4.2)

42/4.5 x 4.2/42

4.2/4.5

42/45

14/15

Answer: A
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Re: Jack and Jill are marathon runners. Jack can finish a marathon (42 km)   [#permalink] 04 Apr 2019, 18:51
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