A canteen spends ₹1,80,000 a month on food for 300 people. Next month its food outlay goes up by 26% while the number of people it feeds goes up by 20%. What is the change in the outlay per person?

Now: 1,80,000/300 = ₹600 per person. Next month: outlay = $1,80,000\times 1.26$ = ₹2,26,800 for $300\times 1.20=360$ people, that is 226800/360 = ₹630 per person. The change is 30/600 = 5%. Shortcut: 1.26/1.20 = 1.05, because a per-person figure DIVIDES the two changes rather than multiplying them. 'A rise of 6%' subtracts the rates (26 - 20), which would only work if the two moved on the same base. 'A rise of 26%' quotes the outlay rise, and 'a fall of 5%' flips the sign.