Question

A 30% chemical solution I is mixed with other solution II of same amount having a% concentration chemical. The resultant mixture is mixed with 60% chemical solution in ratio of 1 ∶ 3. The concentration of chemical in resultant solution is 55% then find the value of a.
1. 45
2. 60
3. 50
4. 40

Answer 1

Correct Answer - Option 3 : 50

Calculation:

Let concentration of chemical in resultant mixture of I and II be m%.

Using rule of alligation,

⇒ 1 ∶ 3 = (60 - 55) ∶ (55 - m)

⇒ 55 - m = 15

⇒ m = 40%

Using rule of alligation,

⇒ 1 ∶ 1 = (a - 40) ∶ (40 - 30)

⇒ a - 40 = 10

⇒ a = 50%

∴ The concentration of chemical in solution II is 50%.

a% is concentration of chemical in solution II.

M is the chemical concentration in resultant mixture of solution I and II.