A shop marks a geyser 60% above what it cost, sells it at a discount of 20% on that marked price, and then charges the customer GST of 12% on the discounted price, every rupee of which is passed on to the government. The shop's profit percent on the geyser is:

Take the cost as ₹100. The marked price is ₹160 and the discounted price is $160\times 0.80$ = ₹128, so the shop keeps ₹128 and its profit is 28%. The GST never belongs to the shop, so it cannot enter the profit at all. (Counting the customer's outlay of $128\times 1.12$ = ₹143.36 as the shop's revenue gives 43.36%; adding and subtracting the rates as 60 − 20 = 40 or 60 − 20 + 12 = 52 treats percentages sitting on three different bases as though they shared one.)