Jhanvi stole some whisky from a bottle which her father had kept in the cupboard. This bottle of whisky contained 40% alcohol. Jhanvi replaced what she drank by another brand of whisky which contained only 20% alcohol. The whisky in the bottle now has only 30% alcohol. What fraction of the original quantity from the bottle did John steal?
Explanation:
Let the initial quantity of bottle be 1 liter. Let the quantity of whisky Jhanvi stole = s liter. Now, quantity of whiskey left in the bottle = (1 - s) liter while quantity of 20% whiskey added = s liter
By applying rule alligation:
Quantity of whisky left with 40% alcoholQuantity of whisky with 20% alcohol = 1010 = 11
∴ 1-ss = 11
⇒ s = 1/2
∴ Jhanvi adds 1/2 of the 20% alcohol whisky.
This means that she drank half of the original bottle of whisky.
Hence, option (a).
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