DRDO Multi tasking staff Model paper 4

Sum of ratios = 3 + 7 = 10
1 kg of wheat mixture contains = (3/10) × 1 = 0.3 kg of wheat costing Rs. 20 per kg
1 kg of wheat mixture contains = (7/10) × 1 = 0.7 kg of wheat costing Rs. 15 per kg
Cost price of 1 kg wheat mixture = (0.3 × 20) + (0.7 × 15) = 6 + 10.5 = Rs. 16.5
Profit earned = 9.09% of 16.5 = 1/11 × 16.5 = Rs. 1.5 per kg
∴ Selling price = cost price + profit = 16.5 + 1.5 = Rs. 18 per kg