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A type A machine can complete a job in 5 hours and a type B [#permalink]

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01 Dec 2005, 06:40

1

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A

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Difficulty:

25% (medium)

Question Stats:

73% (01:57) correct
27% (01:27) wrong based on 220 sessions

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A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

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01 Dec 2005, 08:40

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BG wrote:

Can you, please elaborate on the meaning of" together and independently" Thanx

I was also initially confused by such verbiage. However, this phrasing isn`t just Kaplish, it appears over and over again in various prep materials, so just accept it as "the machines/people/computers etc. work at their full capacity without complementing each other."

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

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01 Dec 2005, 09:41

GMATT73 wrote:

remgeo wrote:

GMATT73 wrote:

remgeo wrote:

I am also getting 10/7

2*1/5 + 3*1/10 = 10/7

Even with the edit, you are still missing a step.

2*1/5 + 3*1/7 = 29/35

Ans = 35/29

I still cant see what step I missed

The step highlighted in red. When did you decide to include it?

Well, I had included that earlier as well.
10/7 was my conclusion 2/5 + 3/10 was the evidence The assumption which is hidden was that I had taken the reverse of 7/10 to get the answer

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

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02 Dec 2005, 16:48

Basic formula for the rate 1/a+1/b+1/c.....=1/Z time=Z

Rate for is A 1/5 and B works at the rate 1/7; 2A=2/5 and 3B=3/7

2/5+3/7=29/35 Flip it. 35/29. That Kaplish stuff can only appear at the beginning of Math section. Actual test questions appear to be much harder than that.
_________________

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

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26 Sep 2014, 12:50

A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?

--just remember rate*time=job Lets consider they both need to type for t hours to get the job done..

So, rate*time=job (Here job is 1 as it needs to be completed) rate for type A machine =1/5 -- effective rate for 2 machines =2/5 similarly for type B machine effective rate for 2 machines =3/7

Finally we have, (2/5)*t + (3/7)*t=1 t(29/35)=1 t=35/29

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

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10 Oct 2016, 06:54

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Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

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10 Oct 2016, 07:00

GMATT73 wrote:

A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?

A. 1/5 B. 29/35 C. 5/6 D. 35/29 E. 35/12

Let the total work be 35 ( LCM of 5 & 7 )

So, Efficiency of type A machines = 35/5 => 7 Efficiency of type A machines = 35/7 => 5

Quote:

How many hours will it take 2 type A machines and 3 type B machines working together

Combined efficiency will be -

Type A = 2*7 => 14 Type B = 3*5 => 15

Total efficiency is 14 + 15 = 29

So, Time taken will be 35/29 Hence correct answer will be (D) 35/29 _________________

Thanks and Regards

Abhishek....

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