A shopkeeper sells a watch for Rs. 540, losing 10%. Find the cost price. MCQ with Answer and Explanation

Explanation:
CP = 330 / 1.1 = 300.

Explanation:
Total CP = 100*10 = 1000. SP = 80*12 + 20*8 = 960 + 160 = 1120. Profit = 120, profit% = 12%? Wait 120/1000*100=12%, not in options. Let's check: actually 80*12=960, 20*8=160, total SP=1120, CP=1000, profit=120, profit%=12%. But option A says 4%. That's wrong. Let's recalc: maybe he sells 80 at Rs.12 each (960) and remaining 20 at Rs.8 each (160) total 1120, profit 120, 12%. Not in options. So this question is flawed. Delete and regenerate.

Explanation:
Let CP of 1 pen = 1. CP of 12 pens = 12. SP of 12 pens = CP of 15 pens = 15. Profit = 15 - 12 = 3. Profit percentage = (3 / 12) * 100 = 25%.