10 litres of concentrated acid containing 75% of acid and rest water is mixed with X litres of diluted acid containing 40% of acid and rest water. If the final mixture contains 60% of acid then value of X is :

7.5 litres

The correct answer is Option (1) → 7.5 litres

Given,

• 10 L of concentrated acid contains 75% acid & 25% water
• X L of Diluted acid contains 40% acid and 60% water
• Final mixture contains 60% acid

Acid in concentrated solution = $10 × 0.75 = 7.5 L$

Acid in diluted solution = $X × 0.40 = 0.40X\, L$

∴ Total acid in final mixture,

$⇒7.5+0.40X=0.60(10+X)$

$⇒1.5=0.20X$

$⇒X=7.5L$