A mixture of 70 litres of Fruit Juice and water contains 10% water. How many litres of water should be added to the mixture so that the mixture contains 12.5% water?

Step 1: Understand the given

Total mixture = 70 litres
Water = 10% of 70 = 7 litres
Fruit juice = 70 - 7 = 63 litres

Step 2: Let x litres of water be added

New water quantity = 7 + x
New total mixture = 70 + x

Step 3: Set up the equation

Water should be 12.5% of total mixture:

(7 + x) / (70 + x) = 12.5% = 0.125

Step 4: Solve the equation

7 + x = 0.125 × (70 + x)

7 + x = 8.75 + 0.125x

x - 0.125x = 8.75 - 7

0.875x = 1.75

x = 1.75 / 0.875 = 2

Answer: 2 litres of water should be added.