how many liters of a 20% alcohol solution must be mixed with 20 liters of a 70% solution to get a 40% solution

30 liters of solution must be mixed.

Step-by-step explanation:

Given:

Amount of solution (70%) = 20 Liters

Amount of 20% alcohol solution = A

Find:

Amount of 20% alcohol solution to get 40% solution

Computation:

Amount of 20% alcohol solution to get 40% solution :

⇒ 20% (A) + 70% (20) = 40% (A + 20)

⇒ 0.2 A + 14 = 0.4 A + 8

⇒ 14 - 8 = 0.4 A - 0.2 A

⇒ 6 = 0.2 A

⇒ A = 30 Liter

30 liters of solution must be mixed.