Sudha buys 40 second-hand stools for ₹10000 and spends ₹2000 on repairing them. She sells 30 of them at ₹420 each and the remaining 10 at ₹240 each. Her profit percent is:

Her outlay is 10000 + 2000 = ₹12000. Her takings are $30\times 420+10\times 240=12600+2400=$ ₹15000, so the profit is ₹3000 on ₹12000 = 25%. (Leaving the repair bill out gives 5000/10000 = 50%, and dividing the ₹3000 profit by the ₹15000 received instead of the cost gives 20%.)