The weighing balance of a greengrocer weighs 10% less than its actual weight. Still, he marks up his vegetables to get an overall profit of 20%. What is the markup percentage on the cost price?

Greengrocer weighs 10% less, so customer gets 0.9 units but pays for 1 unit. For 20% profit overall: Selling Price should be 1.2 × Actual Cost. If cost of 1 unit = C, he gives 0.9 units. Effective cost to him per unit sold = 0.9C. He needs SP = 1.2C, so markup = (1.2C - 0.9C)/0.9C = 0.3C/0.9C = 1/3 = 33.33% on his cost. But this is on CP, so markup percentage = 33.33% of CP. Wait, let me reconsider. Let actual CP = 100. He gives 90 units but sells as 100. His CP for what he sells = 90. He wants 20% profit on actual CP = 100, so SP = 120. Markup on his CP = (120-90)/90 = 30/90 = 33.33%. Hmm, options are 4, 5, 6, 8%. Let me try: Actual CP of 1 unit = 100. He gives 0.9 unit. His CP = 90. He sells at some markup on 90 to get 20% on 100. SP = 120. Markup = 120 - 90 = 30. Percentage = 30/90 = 33.33%. This doesn't match options. Let me reconsider interpretation. If he marks up on cost price meaning on the marked weight: He sells 100 units (marked) but gives 90. To get 20% profit overall on actual: SP should be 120 for 100 marked. CP of 90 actual = 90. So SP = 120. Markup = 120 - 90 = 30. As percentage of CP = 30/90 = 33.33%. Still not matching. Perhaps markup on what he shows: If marked price = M, actual weight = 0.9M, CP = 0.9M. Profit = 20% of CP = 0.18M. So M = CP + profit + markup = 0.9M + 0.18M + markup. This doesn't work. Let me try differently: Let CP of 1kg = 100. He gives 0.9kg. His CP = 90. He wants 20% profit, so revenue should be 108. But he sells as 1kg, so SP = 108. Markup = 108 - 90 = 18. Percentage = 18/90 = 20%. Still not matching. I think the question means: His scale shows 10% less. So when he thinks he's selling 1kg, he's actually giving 1.1kg. Let me try: Marked weight = 100, actual = 110. CP = 110. He wants 20% profit, so SP = 132. But he sells at marked 100, so price per unit marked = 132/100 = 1.32. If CP per unit = 110/100 = 1.1, then markup = (1.32 - 1.1)/1.1 = 0.22/1.1 = 20%. Still not 8%. I'll check with C: 8%. If markup is 8% on CP: SP = 108 (for 100 marked). CP = 90 (actual given). Profit = 108 - 90 = 18. Profit% = 18/90 = 20%. This works! Markup 8% on CP gives SP = 108, profit = 18, profit% = 20% on actual CP of 90. But wait, profit is 18 on 90 = 20%. Yes! So answer C is correct.