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# a+d or b+c

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a+d or b+c [#permalink]  05 Sep 2018, 14:10
00:00

Question Stats:

75% (00:56) correct 25% (00:26) wrong based on 16 sessions
$$\frac{a}{b} = \frac{3}{7} = \frac{c}{d}$$

 Quantity A Quantity B $$a+d$$ $$b+c$$

A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
[Reveal] Spoiler: OA

Last edited by Carcass on 06 Sep 2018, 02:13, edited 1 time in total.
Edited by Carcass
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Re: a+d or b+c [#permalink]  07 Sep 2018, 06:22
Anyone?
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Re: a+d or b+c [#permalink]  07 Sep 2018, 08:38
Expert's post
Actually $$\frac{a}{b}=\frac{3}{7}$$ AND $$\frac{c}{d}=\frac{3}{7}$$

In the first one, a is a multiple of 7 and b of 3

In the second one, c is a multiple of 7 and d of 3.

Now, a=14 and d=6 and which in QA is 21

Then, c=21 and d= 9 so in QB is 30 So the answer is B.

However, a =35 and b=15 and QA is 50

c=7 and d = 3 and QB is 10 So the answer is A. Not sufficient information to have a clear and definitive answer.

The OA is D.

Hope this helps
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Re: a+d or b+c [#permalink]  07 Sep 2018, 14:28
Carcass wrote:
Actually $$\frac{a}{b}=\frac{3}{7}$$ AND $$\frac{c}{d}=\frac{3}{7}$$

In the first one, a is a multiple of 7 and b of 3

In the second one, c is a multiple of 7 and d of 3.

Now, a=14 and d=6 and which in QA is 21

Then, c=21 and d= 9 so in QB is 30 So the answer is B.

However, a =35 and d=15 and QA is 50

c=7 and d = 3 and QB is 10 So the answer is A. Not sufficient information to have a clear and definitive answer.

The OA is D.

Hope this helps

I am confused. You seem to have erroneously typed d multiple times. Also, I have a doubt that why 14 and 6, like why can't it be different multiples of numbers?
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Re: a+d or b+c [#permalink]  07 Sep 2018, 16:24
Expert's post
Yes, sorry in the second disprove statement is not d=15 but b=15. Just typo.

As for your doubt, yes they can be whichever multiple you wanna pick. Mine were just a few examples.

I.E. a/b=3/7 cross multiply and 7a=3b

a is a multiple of 7 and b is a multiple of 3.

Ask for further assistance
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Re: a+d or b+c [#permalink]  07 Sep 2018, 23:27
Carcass wrote:
Yes, sorry in the second disprove statement is not d=15 but b=15. Just typo.

As for your doubt, yes they can be whichever multiple you wanna pick. Mine were just a few examples.

I.E. a/b=3/7 cross multiply and 7a=3b

a is a multiple of 7 and b is a multiple of 3.

Ask for further assistance

So in solving I have to take the same multiples of each other?
Like 7*2 and 3*2
or 7*25 and 3*25
or both can be different, larger or smaller?
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Re: a+d or b+c [#permalink]  07 Sep 2018, 23:57
Expert's post
Multiple of 7a are

7/14/21/28/35.......................

Multiple factors can be also technically negative. However, for the GRE purpose they are considered only positive.

This concept is mentioned in the ETS GRE Math Conventions PDF https://www.ets.org/s/gre/pdf/gre_math_conventions.pdf

Regards
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Re: a+d or b+c [#permalink]  08 Sep 2018, 00:45
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In this kind of questions, you could just give them a value. If a b; c d are 3 7; 3 7respectively ,then Qa and Qb are equal. But if they 3 7；6 14 respectively，Qa and Qb are not equal. Then the answer must be D.
Re: a+d or b+c   [#permalink] 08 Sep 2018, 00:45
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