alphonsa wrote:

In what ratio should a mixture of milk and water in the ratio of 3:4 be mixed with another mixture of milk and water in the ratio 5:2 so that the resultant mixture contains equal quantities of milk and water?

A) 3:1

B) 3:5

C) 7:8

D) 7:9

E) 9:11

We can let the ratio of milk to water in the first mixture be 3x : 4x in which 3x and 4x are the weights of the milk and water, respectively. (Notice the weight of the first mixture will be 3x + 4x = 7x.)

Similarly, we can let the ratio of milk to water in the second mixture be 5y : 2y in which 5y and 2y are the weights of the milk and water, respectively. (Notice the weight of the second mixture will be 5y + 2y = 7y.)

Thus we need:

3x + 5y = 4x + 2y

3y = x

Since x = 3y, the weight of the first mixture is 7x = 7(3y) = 21y. Thus, the ratio in weight of the first mixture to the second mixture is 21y : 7y = 3 : 1.

Answer: A

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Head of GMAT Instruction

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