A society's monthly outlay of ₹80,000 goes on just two heads: ₹50,000 on staff pay and ₹30,000 on fuel. Staff pay is being raised by 18% and the monthly outlay must stay at ₹80,000. By what per cent must the fuel spending be cut?

Staff pay becomes $50,000\times 1.18$ = ₹59,000, so fuel must come down to 80,000 - 59,000 = ₹21,000. The cut of ₹9,000 is measured on the fuel head's own ₹30,000: 9000/30000 = 0.30 = 30%. 18% assumes the two heads swing by matching per cents, but they sit on unequal bases - the smaller head must give up a bigger share. 11.25% measures the ₹9,000 against the whole ₹80,000 outlay. 42.86% is 9000/21000, measured against the reduced fuel figure instead of the earlier one.