Question

how much water must be added to bucket which contains 40 litres of milk at a cost price of Rs.3.50/litre so that cost price of milk reduces to Rs. 2/l​

Answer 1

30 litres water must be added to the bucket which contains 40 litres of milk.

We have to find the amount of water must be added to bucket which contains 40 litres of milk at a cost price of Rs. 3.50/litre so that cost price reduces to Rs. 2/litre.

“The money used to buy 40 litres of milk remains constant after adding the water.”

amount of money used to buy 40 litres of milk = amount of milk × rate

= 40 litres × Rs. 3.5/litre

= Rs. 140

let the amount of water is added to milk is x litre.

then, total volume of mixture = (40 + x) litre.

now its cost price reduces to Rs. 2/litre.

so total money used to the mixture = (40 + x) × 2.

As initial money must be the final money.

∴ 140 = 2(40 + x)

⇒70 = 40 + x

⇒x = 30

Therefore 30 litres of water must be added to the bucket.