Question 46

How many litres of water should be added to a 30 litre mixture of milk and water containing milk and water in the ratio of 7 : 3 such that the resultant mixture has 40% water in it ?

Solution

Quantity of milk in 30 l mixture = $$\frac{7}{3} \times 30 = 21$$ litre

Quantity of water = $$30 - 21 = 9$$ litre

Let the quantity of water to be added = $$x$$ litre

Acc to ques,

=> $$\frac{9 + x}{30 + x} = \frac{40}{100}$$

=> $$\frac{9 + x}{30 + x} = \frac{2}{5}$$

=> $$45 + 5x = 60 + 2x$$

=> $$5x - 2x = 60 - 45 = 15$$

=> $$x = \frac{15}{3} = 5$$ litre

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