Correct Answer - Option 3 : 50 litres
Calculation:
The cost price of a mixture of chemical and water = 250 × 100/125 = Rs. 200
Cost price of water added = Rs. 0
Using rule of alligation,
Ratio of chemical to water = (200 - 0) ∶ (240 - 200) = 5 ∶ 1
Total quantity of mixture = 10 × 6/1 = 60 litres
∴ Quantity of chemical he bought at Rs. 240 = 5/6 × 60 = 50 litres
(Quantity of expensive item)/(Quantity of cheaper item) = (Mean Price - Price of cheaper item)/ (Price of expensive item - Mean price)