MarceloBR wrote:
If m, r, x and y are positive, is the ratio of m to r equal to the ratio of x to y?
(1)the ratio of m to y is equal to the ratio of x to r.
(2)the ratio of m+x to r+y is equal to the ratio of x to y.
We can rephrase this as . . .
REPHRASED target question: Does m/r = x/y?
We may find it useful to take the equation m/r = x/y and cross-multiply to get my = rx. This allows us to rephrase the target question in one more way . . .
RE-REPHRASED target question: Does my = rx?
Aside: We have a free video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Statement 1: The ratio of m to y is equal to ratio of x to r
In other words, m/y = x/r
This LOOKS similar to m/r = x/y (one of our target questions), but it is not the same.
There are several values of m, r, x and y that satisfy this condition. Here are two:
Case a: m = r = x = y = 1, in which case
m/r = x/y
Case b: m = 1, y = 2, x = 3 and r = 6, in which case
m/r ≠x/y
Since we cannot answer the
REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: The ratio of m+x to r+y is equal to the ratio of x to y.
In other words, (m+x)/(r+y) = x/y
Cross multiply to get: y(m+x) = x(r+y)
Expand: ym + yx = xr + xy
Subtract xy from both sides to get:
ym = xy
Perfect, we've shown that
ym = xy, and this is one of our REPHRASED target questions.
Since we can answer the
RE-REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer =
B
Cheers,
Brent
For even more information on rephrasing the target question, you can read this article I wrote for BTG:
https://www.beatthegmat.com/mba/2014/06/ ... t-question
