Ratios - Tricky one

[classicbikash]

DS:
What is the ratio of r to s?

(1) r + s = 7

(2) r(square) - s(square) = 7

Soln:
In the MGMAT the answer mentioned is C (Both are required to answer the question.)
However I am not convinced.
I think the answer should be B.(Choice B is sufficient).
Reason:
1 4 9 16 25
The difference is 7 only when 16 - 9 = 7
so the ratio is 4/3 hence B.

Can you please help me with this? Should the answer be B or C.
If c can you give me few examples to explain it.

[djamrose]

Squaring the terms does not tell the sign of r or s. Either one could be negative. If the signs where the same (neg or pos) the ratio would be 4/3 but if either r or s is negative the ratio would be -4/3. Therefore statement 2 (or B) is not sufficient. Statement 1 tells you they both are positive. Therefore both 1&2 are required. It looks like C is correct to me.

hope that helps

[ilakshmir]

I agree with the answer C. It is not mentioned that r,s are integers. So r,s, can take several values to satisfy statement B.

[Ben Ku]

Both ilakshmir and djamrose have excellent points in this question. The problem tells us nothing about r and s, so we cannot assume anything about them. They can be positive or negative, integers or non-integers.

Be careful about making extra assumptions in GMAT questions.