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30 litres of salt solution contains 5% salt. How many litres of water must be added so as to get a resulted solution containing 3% salt? A. 20 litres B. 25 litres C. 30 litres D. 35 litres

30 litres of salt solution contains 5% salt. How many litres of water must be added so as to get a resulted solution containing 3% salt? A. 20 litres B. 25 litres C. 30 litres D. 35 litres Correct Answer A

Given:

30 litres of salt solution contains 5% salt

Calculation:

Let the quantity of water added be x litres

Initial quantity of water = (95/100) × 30 = 28.5 litre

If the x litre of water is added then

⇒ Percentage of water = (97/100) × (30 + x) = 29.1 + 097x 

Now total quantity of water after adding x litres of water 

⇒ 28.5 + x = 29.1 + 0.97x

⇒ 0.03x = 0.6

⇒ x = 20 litres

∴ 20 litres of water is added 

Alternate Method

Quantity of salt = 30 × (5/100) = 1.5

Let x lt of water is added.

Hence, 

1.5/(30 + x) × 100 = 3

⇒ 30 + x = 50

⇒ x = 20 lt. 

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