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M15-09

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M15-09  [#permalink]

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New post 16 Sep 2014, 00:55
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A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

92% (01:19) correct 8% (01:51) wrong based on 48 sessions

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Math Expert
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Re M15-09  [#permalink]

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New post 16 Sep 2014, 00:55
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Re: M15-09  [#permalink]

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New post 09 Jan 2017, 05:58
Given that A/B=(A+6)/(B+15), cross multiply to get the ratio between B and A. The answer comes out to be 2.5 i.e. option C
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Re: M15-09  [#permalink]

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New post 22 Nov 2017, 00:00
Can we back solve this question anyway?
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M15-09  [#permalink]

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New post 05 Nov 2018, 10:37
santro789 wrote:
Can we back solve this question anyway?


Hey santro789

Sure u can! But it is just too time consuming.

When back solving always remember to start from the middle option so that you know wether u should test higher values or lower values.
Luckily in this question 2.5 is the middle value and we can arrive at the AC quick.
So since it is a fraction it wont matter if u take A/B as 2/5 or 200/500. Just make sure B/A is equal to 2.5 because we are testing for it.
You will see that by adding the A and B with 6 and 15 will always give us \(\frac{2}{5}\).
Example - \(\frac{2}{5}\) is \(\frac{2+6}{5 +15}\) = \(\frac{8}{20}\) = \(\frac{2}{5}\).
Hence C is the option.

Hope it helps!
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Re: M15-09  [#permalink]

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New post 23 Nov 2018, 11:29
Bunuel How can we get from 6B=15A to B/A=15/6 without knowing that A is not 0? Thanks!
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Re: M15-09  [#permalink]

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New post 15 Jun 2019, 23:26
Hi Bunuel,

Is the below approach correct.

As mentioned in the question the ratio will not change if 6 is added to A and 15 is added to B.
Thus 6/15 will have the same ratio as A/B.
So to find B/A => just do 15/6 =2.5

Thanks
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Re: M15-09   [#permalink] 15 Jun 2019, 23:26
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