[ Percentage and ratio problems ]

How many pounds of grain need to be milled to have exactly 100 pounds of flour left after paying for the work - 10% of the milling?

There are no losses during milling.

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Think about what part of the payment will be from the final revenue, not the initial one.

## Solution

The remaining 100 pounds constitute $90\%$ (that is, $9/10$) of the weight of the grain. Therefore, the weight of the grain was $100 \cdot 10 / 9 = 111^{1} / 9$ pounds.

## Answer

$111 \frac{1}{9}$ pounds.