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When a/b=1.2, (a-b)/(a+b)=?

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When a/b=1.2, (a-b)/(a+b)=? [#permalink]

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When a/b=1.2, (a-b)/(a+b)=?

A. \(\frac{1}{15}\)
B. \(\frac{1}{11}\)
C. \(\frac{1}{9}\)
D. \(\frac{3}{8}\)
E. \(\frac{1}{3}\)
[Reveal] Spoiler: OA

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Re: When a/b=1.2, (a-b)/(a+b)=? [#permalink]

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New post 24 Apr 2017, 02:41
When a/b=1.2, (a-b)/(a+b)=?

Divide numerator and denominator by b.

we get, (a/b-1)/(a/b+1) = (1.2-1)/(1.2+1) = 0.2/2.2 = 0.1/1.1 = 1/11

Hence, answer is B.
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Re: When a/b=1.2, (a-b)/(a+b)=? [#permalink]

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New post 26 Apr 2017, 00:17
==> From a/b=1.2=6/5, if you substitute a=6 and b=5, you get (a-b)/(a+b)=(6-5)/(6+5)=1/11.

Therefore, the answer is B.
Answer: B
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Re: When a/b=1.2, (a-b)/(a+b)=? [#permalink]

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New post 26 Apr 2017, 00:22
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MathRevolution wrote:
When a/b=1.2, (a-b)/(a+b)=?

A. \(\frac{1}{15}\)
B. \(\frac{1}{11}\)
C. \(\frac{1}{9}\)
D. \(\frac{3}{8}\)
E. \(\frac{1}{3}\)


Hey,

We can also apply componendo and dividendo to solve this question. :)

    \(\frac{a}{b} = \frac{1.2}{1}\)

    \(\frac{(a - b)}{(a + b)} = \frac{(1.2 - 1)}{(1.2 + 1)}\)

    \(\frac{(a - b)}{(a + b)} = \frac{0.2}{2.2}\)

    \(\frac{(a - b)}{(a + b)} = \frac{1}{11}\)

Hence correct answer is Option B.


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When a/b=1.2, (a-b)/(a+b)=? [#permalink]

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New post 28 Apr 2017, 13:44
MathRevolution wrote:
When a/b=1.2, (a-b)/(a+b)=?

A. \(\frac{1}{15}\)
B. \(\frac{1}{11}\)
C. \(\frac{1}{9}\)
D. \(\frac{3}{8}\)
E. \(\frac{1}{3}\)

\(\frac{a}{b}\) = 1.2

Multiply both sides by b

a = 1.2b

Let b = 10 (Choose a number that will yield an integer when multiplied by 1.2)

So a = (1.2)(10) = 12

(a-b) = 12 - 10 = 2
(a+b) = 12 + 10 = 22

\(\frac{(a-b)}{(a+b)}\) ==> \(\frac{2}{22}\) = \(\frac{1}{11}\) Answer: B
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Re: When a/b=1.2, (a-b)/(a+b)=? [#permalink]

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New post 29 Apr 2017, 08:01
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MathRevolution wrote:
When a/b=1.2, (a-b)/(a+b)=?

A. \(\frac{1}{15}\)
B. \(\frac{1}{11}\)
C. \(\frac{1}{9}\)
D. \(\frac{3}{8}\)
E. \(\frac{1}{3}\)


We are given:

a/b = 1.2

a = 1.2b

We need to determine the value of (a - b)/(a + b).

(a - b)/(a + b) = (1.2b - b)/(1.2b + b) = 0.2b/2.2b = 0.2/2.2 = 2/22 = 1/11

Answer: B
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Re: When a/b=1.2, (a-b)/(a+b)=?   [#permalink] 29 Apr 2017, 08:01
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