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# It takes Jack 2 more hours than Tom to type 20 pages. If

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Intern
Status: never give up on yourself
Joined: 14 Apr 2018
Posts: 5
WE: Corporate Finance (Accounting)
Re: It takes Jack 2 more hours than Tom to type 20 pages. If  [#permalink]

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20 Jun 2018, 04:53
VeritasPrepKarishma wrote:
Barkatis wrote:
It takes Jack 2 more hours than Tom to type 20 pages. If working together, Jack and Tom can type 25 pages in 3 hours, how long will it take Jack to type 40 pages?

5
6
8
10
12

Can anyone explain the method to work with such problems ? Cause I always get them wrong !
And if you know any similar questions, please share. Thanks

You can solve equations like the one given below using some logic. Even if you do not have options, you can still get your answer very easily. You don't really need to make a quadratic.

$$\frac{20}{t} + \frac{20}{(t+2)} = \frac{25}{3}$$

Look at the right hand side of the equation. The fraction is in the lowest form. So you looking for a 3 somewhere in the denominator. Also note that 25/3 is a little more than 8.
Can 't' be 3? No, because 20/3 + 20/5 is a little more than 10.
Can 't+2' be 3? No, because then t = 1 and the sum on the left hand side will be more than 20.
Can 't+2' be 6 instead? 20/4 + 20/6 = 25/3
So t must be 4 and t+2 must be 6.

can you please explain what is wrong with my method
rate of jack =1/x
rate of tom=1/x-2
working together they will take=1/x + 1/x-2 = 1/3
i am not getting the correct answer
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8397
Location: Pune, India
Re: It takes Jack 2 more hours than Tom to type 20 pages. If  [#permalink]

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20 Jun 2018, 05:35
Abhishekgmatfit wrote:
VeritasPrepKarishma wrote:
Barkatis wrote:
It takes Jack 2 more hours than Tom to type 20 pages. If working together, Jack and Tom can type 25 pages in 3 hours, how long will it take Jack to type 40 pages?

5
6
8
10
12

Can anyone explain the method to work with such problems ? Cause I always get them wrong !
And if you know any similar questions, please share. Thanks

You can solve equations like the one given below using some logic. Even if you do not have options, you can still get your answer very easily. You don't really need to make a quadratic.

$$\frac{20}{t} + \frac{20}{(t+2)} = \frac{25}{3}$$

Look at the right hand side of the equation. The fraction is in the lowest form. So you looking for a 3 somewhere in the denominator. Also note that 25/3 is a little more than 8.
Can 't' be 3? No, because 20/3 + 20/5 is a little more than 10.
Can 't+2' be 3? No, because then t = 1 and the sum on the left hand side will be more than 20.
Can 't+2' be 6 instead? 20/4 + 20/6 = 25/3
So t must be 4 and t+2 must be 6.

can you please explain what is wrong with my method
rate of jack =1/x
rate of tom=1/x-2
working together they will take=1/x + 1/x-2 = 1/3
i am not getting the correct answer

How does 1/x + 1/x-2 equal 1/3?

$$\frac{1}{x} + \frac{1}{(x-2)} = \frac{(2x - 2)}{x(x - 2)} = \frac{5}{12}$$

Note how you get 5/12 - The combined rate is 25 pages in 3 hrs. But initially our work done was 20 pages which would then be done in (4/5)*3 = 12/5 hrs. So combined rate is 5/12.

When you solve the above, you get x = 6.

So Jack types 20 pages in 6 hrs. He will type 40 pages in 12 hrs.
_________________

Karishma
Veritas Prep GMAT Instructor

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Re: It takes Jack 2 more hours than Tom to type 20 pages. If &nbs [#permalink] 20 Jun 2018, 05:35

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# It takes Jack 2 more hours than Tom to type 20 pages. If

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