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# Ferman can do a job in 6 days and Kelly can do the same job

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Intern
Joined: 09 Jul 2013
Posts: 10
Concentration: Human Resources, Entrepreneurship
Schools: ISB '14
Ferman can do a job in 6 days and Kelly can do the same job  [#permalink]

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06 Sep 2013, 11:13
9
12
00:00

Difficulty:

35% (medium)

Question Stats:

77% (02:36) correct 23% (02:53) wrong based on 266 sessions

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Ferman can do a job in 6 days and Kelly can do the same job in 8 days. They both undertake the job for $640. With the help of Mary, they finished it in 3 days. How much was paid to Mary? A.$75
B. $80 C.$85
D. $100 E.$120
Intern
Joined: 14 Aug 2013
Posts: 34
Location: United States
Concentration: Finance, Strategy
GMAT Date: 10-31-2013
GPA: 3.2
WE: Consulting (Consumer Electronics)
Re: Ferman can do a job in 6 days and Kelly can do the same job  [#permalink]

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06 Sep 2013, 11:44
2
Ferman takes 6 days to complete the work, so he does 1/6th of the work in one day
similarly kelly does 1/8th of the work in one day.
Given they worked for 3 days=> 3(1/6+1/8)=7/8th of the work is done by Ferman and Kelly in 3 days
Remaining 1/8th of the work is done with the help of Mary.
So Mary share is proportional the amount of work done=> 1/8th of 640=80$Verbal Forum Moderator Joined: 10 Oct 2012 Posts: 613 Re: Ferman can do a job in 6 days and Kelly can do the same job [#permalink] ### Show Tags 06 Sep 2013, 11:47 1 1 aparnaharish wrote: Ferman can do a job in 6 days and Kelly can do the same job in 8 days. They both undertake the job for$640. With the help of Mary, they finished it in 3 days. How much was paid to Mary?

A. $75 B.$80
C. $85 D.$100
E. $120 Rate of doing work for Ferman =$$\frac{1}{6}$$ and for Kelly =$$\frac{1}{8}$$. Also, as $$Time*Rate = Work$$, we have $$3*[\frac{1}{6}+\frac{1}{8}+r_{Mary}] = 1$$unit of work Thus,$$r_{Mary} = \frac{1}{3}-(\frac{1}{6}+\frac{1}{8})$$ $$\to r_{Mary} = \frac{1}{24}$$ Thus, work done by Mary in 3 days : $$3* \frac{1}{24}$$ = $$\frac{1}{8}$$ units of work, and as the payment is directly proportional to the work done, the payment for her =$$\frac{640}{8}$$= 80$

B.
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Joined: 26 Feb 2013
Posts: 156
Re: Ferman can do a job in 6 days and Kelly can do the same job  [#permalink]

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25 Sep 2013, 06:21
mau5 wrote:
aparnaharish wrote:
Ferman can do a job in 6 days and Kelly can do the same job in 8 days. They both undertake the job for $640. With the help of Mary, they finished it in 3 days. How much was paid to Mary? A.$75
B. $80 C.$85
D. $100 E.$120

Rate of doing work for Ferman =$$\frac{1}{6}$$ and for Kelly =$$\frac{1}{8}$$. Also, as $$Time*Rate = Work$$,

we have $$3*[\frac{1}{6}+\frac{1}{8}+r_{Mary}] = 1$$unit of work

Thus,$$r_{Mary} = \frac{1}{3}-(\frac{1}{6}+\frac{1}{8})$$ $$\to r_{Mary} = \frac{1}{24}$$

Thus, work done by Mary in 3 days : $$3* \frac{1}{24}$$ = $$\frac{1}{8}$$ units of work, and as the payment is directly proportional to the work done, the payment for her =$$\frac{640}{8}$$= 80$B. Why isn't Mary's rate 1/x ? as in 1 work per x days Manager Joined: 23 May 2013 Posts: 108 Re: Ferman can do a job in 6 days and Kelly can do the same job [#permalink] ### Show Tags 08 Nov 2013, 06:07 Skag55 wrote: Ferman can do a job in 6 days and Kelly can do the same job in 8 days. They both undertake the job for$640. With the help of Mary, they finished it in 3 days. How much was paid to Mary?

Why isn't Mary's rate 1/x ? as in 1 work per x days

you can take it as 1/x too. then work done in 1 day will be

1/6+1/8+1/x = 1/3
1/x = 1/24
so Mary does 1/24 work in 1 day. Hence in 3 days she does 3/24 = 1/8 of work.
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Re: Ferman can do a job in 6 days and Kelly can do the same job  [#permalink]

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16 Apr 2018, 21:41
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Re: Ferman can do a job in 6 days and Kelly can do the same job &nbs [#permalink] 16 Apr 2018, 21:41
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