Linear Equation

Question

Pure acid is to be added to a 10% acid solution to obtain 90L of 37% solution. What amount of each should be used?

Answer 1

Let a = the number of liters of 100% acid and let b = the number of liters of 10% acid

then a + b = 90 & from the other condition (100a + 10b)/(a + b) = 37 or 100a + 10b = 90(37) = 3330

The 2 equations are now a + b = 90 or 100a + 100b = 9000

and 100a + 10b = 3330

Solving the 2 together, we have b = 63 and a = 27