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# If b/a+b

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If b/a+b [#permalink]  08 Jan 2018, 14:27
Expert's post
00:00

Question Stats:

85% (00:35) correct 14% (00:40) wrong based on 28 sessions
If $$\frac{b}{a+b} = \frac{7}{12}$$, then what does $$\frac{a}{b}$$ equal ?

A. $$\frac{7}{19}$$

B. $$\frac{5}{12}$$

C. $$\frac{5}{7}$$

D. $$\frac{7}{5}$$

E. $$\frac{19}{12}$$
[Reveal] Spoiler: OA

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Manager
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Re: If b/a+b [#permalink]  10 Jan 2018, 01:21
1
KUDOS
Lets develop
7(a+b) = 12 b
7 a + 7b = 12b
7a = 5b
7a/b = 5
A/b = 5/7

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Kudos [?]: 1994 [1] , given: 20

Re: If b/a+b [#permalink]  10 Jan 2018, 10:47
1
KUDOS
Expert's post
Carcass wrote:
If $$\frac{b}{a+b} = \frac{7}{12}$$, then what does $$\frac{a}{b}$$ equal ?

A. $$\frac{7}{19}$$

B. $$\frac{5}{12}$$

C. $$\frac{5}{7}$$

D. $$\frac{7}{5}$$

E. $$\frac{19}{12}$$

Here's another approach that uses a often-tested property: (x + y)/z = x/z + y/z

If b/(a+b) = 7/12, then we can also say that (a + b)/b = 12/7

Applying the above property, we can write: a/b + b/b = 12/7
Simplify: a/b + 1 = 12/7
Subtract 1 from both sides to get: a/b = 12/7 - 1
Rewrite 1 as follows: a/b = 12/7 - 7/7
Evaluate: a/b = 5/7

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Re: If b/a+b [#permalink]  11 Jan 2018, 05:51
Re: If b/a+b   [#permalink] 11 Jan 2018, 05:51
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