Question

you need a 35% alcohol solution. on hand you have a 245ml of a 90% alcohol mixture. how much pure water will you need to add to obtain the desired solution

Answer 1

Let the alcohol solution be represented by s

let the quantity of alcohol mixture be represented by m

let the quantity of pure water required be represented by p

35% ( 245 + p) = 90% x 245

0.35 (245 + p) = 0.9 x 245

0.35(245 + p) = 220.5

Divide both sides by 0.35

=> (245 + p) = 220.5 / 0.35

=>245 + p = 630

=>p = 630 -245

=>p = 385 ml

Quantity of pure water required 385 ml