Correct Answer - Option 3 : 49 litres
Solution:
Given:
Oil : Water = 5 : 7
Ratio of oil : kerosene: petrol = 35 : 49 : 18
Amount of oil removed + 21 = Amount of petrol added
Calculation:
Amount of oil removed = 21 - 6
⇒ Amount of oil removed = 15 litres
⇒ Amount of petrol added = 15 + 21
⇒ Amount of petrol added = 36 litres
⇒ Amount of oil in new mixture = 36 × 35/ 18
⇒ Amount of oil in new mixture = 70 litres
⇒ Amount of kerosene in new mixture = 49 × 36/ 18
⇒ Amount of kerosene in new mixture = 98 litres
Total quantity of mixture = 204 litres
⇒ Amount of kerosene in old mixture = 7 × 204/ 12
⇒ Amount of kerosene in old mixture = 119 litres
Difference required is 119 – 70 = 49
∴ required difference is 49 litres