Bunuel
18 litres of pure water was added to a vessel containing 80 litres of pure milk. 49 litres of the resultant mixture was then sold and some more quantity of pure milk and pure water was added to the vessel in the ratio of 2 : 1. If the resultant ratio of milk to water in the vessel was 4 : 1, what was the quantity of pure milk added to the vessel ? (in litres)
(A) 4
(B) 6
(C) 12
(D) 16
(E) 18
Initially, we had: milk = 80, water = 18
Total quantity = 98 litres
Quantity Sold = 49 litres, which is half of the total volume
Thus, each of milk and water would become half their respective volumes; i.e. milk = 40, water = 9
Milk : water added = 2 : 1
Say Milk added = 2x and water added = x
Thus, final milk = 40+2x and water = 9+x
This ratio is 4:1
Hence: (40+2x)/(9+x) = 4/1
x = 2
Thus, milk added = 2x = 4 litres
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