Find the Percentage ???

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Q: If the price of oil increases by 25%, by what percentage should its consumption be reduced so that the total expenditure on oil does not increase ?

Options: (a) 16% (b) 24% (c) 25% (d) 20%

Solution:
When the price increases by 25%, the new price becomes 125 (from 100).
To keep the total cost constant:100 / 125×100 = 80

Thus, consumption must be reduced by 100 - 80 = 20%