Hi All,

This question can be approached in a couple of different ways, depending on how you 'see' the math involved.

We're told that milk is purchased for Rs 6.40/liter, mixed with some water, then the mixture is resold at Rs 8/liter. We're told that this process leads to a 37.5% profit.

37.5% = 3/8, so we're looking for total revenue that is Rs 6.40 + (3/8)(Rs 6.40)....

1/8 of Rs 6.40 = Rs 0.80, so....
3/8 of Rs 6.40 = Rs 2.40

Thus, that one liter of milk (and whatever water is mixed in) has to generate Rs 6.40 + Rs 2.40 = Rs 8.80 of revenue.

Comparing Rs 8 and Rs 8.80, you'll notice that the second number is exactly 10% greater than the first number. Thus, the amount of water that we need to add must be 10% of the volume of milk. A ratio of water:milk of 1:10 is needed.

Final Answer:

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Let y amount of water be added to 1ltr of water , so {8(1+y)-6.4}/6.4 = 37.5/100
So on solving y=1/10
Hence water to milk ratio is 1/10 so ans is A

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