This is a great case to think of mixtures as a "tug of war" between 2 quantities.
Imagine a number line with P standing on 60% trying to "pull" the final mixture towards itself.
Q stands on 10% trying to "pull" the final mixture towards itself.
And the final mixture actually lands on R, which stands at 25%. Q has "pulled" the final mixture 35 away from Q, but P has "pulled" the final mixture only 15 away from R. So the ratio of Q/P = 35/15 = 7/3.
Statement (1) gives us the value of Q = 455. So 455/P = 7/3, so we could solve for "P". SUFFICIENT
Statement (2) gives us R = 650. Since Q+P = 650 and Q/P = 7/3, we'd now have 3 distinct equations with 3 variables, so we'd be able to solve for any variable, including "P". SUFFICIENT.
Each statement is SUFFICIENT -- answer choice (D).
Gene Suhir
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