Grayson, a chemist, has 8 litres of a solution that contains 15% hydrochloric acid(HCI), plus unlimited 5% HCI solution. For a particular experiment, however, he needs to prepare some that contains 12% HCI. How much 5% HCI solution should be added to the 15% HCI solution to get the 12% HCI solution needed for the experiment? Answers:
A) 7.6 litres
B) 10 litres
C) 12.8 litres
D) 3.4 litres
E) 8.2 litres
0.15(8)+0.05x = 0.12(8 + x)   Solve the equation.   0.15(8) + 0.05x = 0.12(8 + x)   1.2 + 0.05x = 0.96 + 0.12x   1.2 – 0.07x = 0.96   -0.07x = -0.24   x ≈ 3.4   Answer is 3.4 litres.
<result>D</result>
Grayson, a chemist, has 8 litres of a solution that contains 15% hydrochloric acid(HCI), plus unlimited 5% HCI solution. For a particular experiment, however, he needs to prepare some that contains 12% HCI. How much 5% HCI solution should be added to the 15% HCI solution to get the 12% HCI solution needed for the experiment?