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Working together, John and Jack can type 20 pages in one hou [#permalink]

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09 Oct 2010, 00:26

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Working together, John and Jack can type 20 pages in one hour. If they would be able to type 22 pages in one hour if Jack increases his typing speed by 25%, what is the ratio of Jack's normal typing speed to that of John?

Working together, John and Jack can type 20 pages in one hour. If they would be able to type 22 pages in one hour if Jack increases his typing speed by 25%, what is the ratio of Jack's normal typing speed to that of John?

1/3 2/5 1/2 2/3 3/5

Lets say John types x pages an hour and Jack types y pages an hour.

We know that x+y=20

Jack increase speed by 25% means he will type 1.25y pages an hour.

So we get x+1.25y=22

We need to know the ratio of Jack's speed to John's speed. This is going to be proportional to the number of pages each can type in an hour, hence (y/x).

Subtracting both : 0.25y=2 so y=8 ... so x=12 (y/x)=2/3

Working together, John and Jack can type 20 pages in one hour. If they would be able to type 22 pages in one hour if Jack increases his typing speed by 25%, what is the ratio of Jack's normal typing speed to that of John?

1/3 2/5 1/2 2/3 3/5

Let the rate of John be \(x\) pages per hour and the rate of Jack \(y\) pages per hour. Then as we can sum the rates and \(rate*time=job\): \((x+y)*1=20\) --> \(x+y=20\);

"They would be able to type 22 pages in one hour if Jack increases his typing speed by 25%": \((x+1.25y)*1=22\) --> \(x+1.25y=22\);

OR: as by increasing the rate of Jack by 25% 2 more pages can be typed in one hour than we can directly write: \(0.25y=2\) --> --> \(y=8\) --> \(x=12\) --> \(\frac{y}{x}=\frac{8}{12}=\frac{2}{3}\).

Re: Working together, John and Jack can type 20 pages in one hou [#permalink]

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07 Nov 2013, 09:17

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Working together, John and Jack can type 20 pages in one hou [#permalink]

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01 Dec 2014, 09:56

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Working together, John and Jack can type 20 pages in one hou [#permalink]

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01 Apr 2015, 11:02

@Bunuel,when do i take rate as 1/x and i/y and when to take it directly as x and y?I took the former and it became quite convoluted while taking the former.

Working together, John and Jack can type 20 pages in one hou [#permalink]

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01 Apr 2015, 21:45

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This post was BOOKMARKED

Barkatis wrote:

Working together, John and Jack can type 20 pages in one hour. If they would be able to type 22 pages in one hour if Jack increases his typing speed by 25%, what is the ratio of Jack's normal typing speed to that of John?

A. 1/3 B. 2/5 C. 1/2 D. 2/3 E. 3/5

so we are told that Jack's 25% typing speed contributes 2 pages , 100% speed would contribute 8 pages in an hours. So JACK types 8 Pages and JOHN types 12 Pages in an hour time.

Ratio of their speed : \(\frac{8}{12} = \frac{2}{3}\) Answer D
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Re: Working together, John and Jack can type 20 pages in one hou [#permalink]

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31 Aug 2016, 06:31

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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