Hi Gmatdecoder,
In mixture questions, if you're not given amounts of each item to work with (in this case, the amount of the 2 detergents), then you can TEST VALUES and use real numbers to solve the problem.
Here, we're told about 2 detergents:
Detergent X = 20% bleach
Detergent Y = 45% bleach
We're told to mix some of each detergent together and end up with a 35% bleach mixture.
Here's how you can TEST VALUES:
Let's say you have 10 oz of Detergent X...
10(20%) = 2 oz bleach
We'll have to mix that with a certain amount of Detergent Y (let's call that Y oz.)
Y(45%) = .45Y oz bleach
Bleach/All = (2+.45Y)/(10 + Y) = .35
2+.45Y = 3.5 + .35Y
.1Y = 1.5
Y = 15
So, we need 15 oz. of Detergent Y to be mixed with 10 oz. of Detergent X to get a combined mixture that is 35% bleach.
The question asks what percent of the final mixture is X?
10/25 = 40%
Final Answer:
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