Question 349274
Let {{{a}}} = liters of pure acid to be added
Let {{{b}}} = liters of 10% solution to be added
given:
(1) {{{a + b = 45}}}
{{{(a + .1b)/45 = .4}}}
{{{a + .1b = 18}}}
(2) {{{10a + b = 180}}}
Subtract (1) from (2)
(2) {{{10a + b = 180}}}
(1) {{{-a - b = -45}}}
{{{9a = 135}}}
{{{a = 15}}}
From (1),
{{{b = 45 - 15}}}
{{{b = 30}}}
15 liters of pure acid and 30 liters of 10% acid solution must be mixed