Question

Nawazudin Siddiqui, a chemist in a petrochemical company has solution A having 50% acid and a solution B containing 25% acid. How much of each should be used to make 20 liters of a 30% acid solution? 
1. 5 liters, 15 liters
2. 4 liters, 16 liters
3. 8 liters, 12 liters
4. 14 liters, 6 liters

Answer 1

Correct Answer - Option 2 : 4 liters, 16 liters

Given∶

Solution A having 50% acid. 

Solution B having 25% acid.

Formula Used∶

Basics Linear Equations.

Calculation∶

Let x liters of 50% solution be mixed with y liters of 25% solution  ∶     

According to question,

x + y = 20      ---(1)

And 50% x + 25% of y = 30% of 20

⇒ 50x/100 + 25y/100 = 30 

× 20/100

⇒ 50x + 25y = 600

⇒ 2x + y = 24      ---(2)

On subtracting eq.(1) from eq.(2), we get

⇒ x = 4

Now put x = 4 in eq.(1)

⇒ x + y = 20

⇒ y = 20 - 4 = 16

∴ 4 liters of 50% solution be  mixed with 16 liters of 25% solution. So, option (2) is the correct answer.