GMAT Prep Question

jaydeer44 · Posted: Fri Mar 21, 2008 4:15 pm Post subject: GMAT Prep Question

Does anyone know the best way to solve this DS problem?

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.

The answer is B.

prachipareekh · Posted: Wed Mar 26, 2008 11:08 pm Post subject:

Remember:

if p/q = r/s then
p+r/q+s = p/q = r/s
p-r/q-s = p/q = r/s
ps = qr

From statement(1): m/y = x/r -- insufficient we cannot find value of m/r
From statement(2): (m+x)/(r+y) = x/y
=> my+xy = xr+xy
=> my = xr
=> m/r = x/y -- sufficient

Hence ans B

moneyman · Posted: Thu Mar 27, 2008 5:27 am Post subject:

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 have to find out if m/r=x/y which means we have to find out if my=xr

(1) is not sufficient because it says m/y=x/r or mr=xy

(2) is SUFFICIENT because it says m+x/r+y=x/y or ym+xy=rx+yx(by cross multiplying)

xy cancels on both sides and we get my=xr