Question

An industrialist has 460 litres of a chemical which is 75% pure. She mixes it with a chemical of the same type but 90% pure so as to obtain a mixture which is 78% pure. Find the amount of the 90% pure chemical used.

Answer 1

⁷⁵/₁₀₀ x 460 = 345
345 + 0.9x = 358.8 + 0.78x
Let 90% pure chemical use x 0.12x=13.8
345 + ⁹⁰/₁₀₀x = 75/100(460 + x)
x = 115 litres