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I was trying to solve this question, couldn't get the start even sadly. The question is following :

Q: A dairyman pays dollar (couldn't get sign working) 6.40 per liter of milk. He adds water and sells the mixture at dollar 8 per liter, thereby making $ 37.5$%$ $ profit. The proportion of water to milk received by the customer is ?

Can anyone give me conceptual method to think of problem and hints to approach it?

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up vote 0 down vote accepted

Just give each unknown a variable and work your way through it. Get used to calculate this way.

Start with X money -> Buy milk -> add water -> sell it -> end up with 1.375*x money

How many liters of milk can you buy with X money? X/6.40.

Now that you have X/6.40 liters of milk, lets add Y liters of water. We will have X/6.40+Y liters of milk now.

Let's sell all our milk thus making a revenue of (X/6.40+Y)*8

Now what? How can you find Y and how can you relate the variable Y with the answer?

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