[GMAT math practice question]
$$When\ \frac{x}{y}=2.6,\ \frac{\left(x-y\right)}{\left(x+y\right)}=?$$
$$A.\ \frac{2}{7}$$
$$B.\ \frac{3}{8}$$
$$C.\ \frac{4}{9}$$
$$D.\ \frac{5}{9}$$
$$E.\ \frac{7}{10}$$
When x/y = 2.6, (x-y)/(x+y)=?
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- Max@Math Revolution
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GIVEN: x/y = 2.6Max@Math Revolution wrote:[GMAT math practice question]
$$When\ \frac{x}{y}=2.6,\ \frac{\left(x-y\right)}{\left(x+y\right)}=?$$
$$A.\ \frac{2}{7}$$
$$B.\ \frac{3}{8}$$
$$C.\ \frac{4}{9}$$
$$D.\ \frac{5}{9}$$
$$E.\ \frac{7}{10}$$
Scan the answer choices....
All of them are in fraction form. So....
Rewrite 2.6 as a fraction: x/y = 2 3/5
Or...: x/y = 13/5
So, let's let x = 13 and y = 5, since these values satisfy the condition that x/y = 13/5
Our goal is to find the value of (x - y)/(x + y)
Plug in x = 13 and y = 5
We get: (x - y)/(x + y) = (13 - 5)/(13 + 5)
= 8/18
= 4/9
Answer: C
Cheers,
Brent
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Yes, that's the way I did it, then there's this way also:Brent@GMATPrepNow wrote:GIVEN: x/y = 2.6Max@Math Revolution wrote:[GMAT math practice question]
$$When\ \frac{x}{y}=2.6,\ \frac{\left(x-y\right)}{\left(x+y\right)}=?$$
$$A.\ \frac{2}{7}$$
$$B.\ \frac{3}{8}$$
$$C.\ \frac{4}{9}$$
$$D.\ \frac{5}{9}$$
$$E.\ \frac{7}{10}$$
Scan the answer choices....
All of them are in fraction form. So....
Rewrite 2.6 as a fraction: x/y = 2 3/5
Or...: x/y = 13/5
So, let's let x = 13 and y = 5, since these values satisfy the condition that x/y = 13/5
Our goal is to find the value of (x - y)/(x + y)
Plug in x = 13 and y = 5
We get: (x - y)/(x + y) = (13 - 5)/(13 + 5)
= 8/18
= 4/9
Answer: C
Cheers,
Brent
Given that X/Y has been specified, can (X-Y)/(X+Y) make direct use of it ?
Divide top and bottom by Y:
= (X/Y-1)/(X/Y+1)
Plug in X/Y=2.6:
(2.6-1)/(2.6+1) = 1.6/3.6 = 16/36 = 4/9
- Max@Math Revolution
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$$\frac{\left(x-y\right)}{\left(x+y\right)}=\frac{\frac{x}{y}-1}{\frac{x}{y}+1}=\frac{\left(2.6-1\right)}{\left(2.6+1\right)}=\frac{1.6}{3.6}=\frac{16}{36}=\frac{4}{9}$$
Therefore, the answer is C.
Answer: C
Therefore, the answer is C.
Answer: C
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