13. When painting the lounge, I used half of a 3 litre can to complete the first coat of paint. I then used two thirds of what was left to complete the second coat. How much paint was left after both coats were complete?
A $150 \mathrm{ml}$
B $200 \mathrm{ml}$
C $250 \mathrm{ml}$
D $500 \mathrm{ml}$
E $600 \mathrm{ml}$
Solution: $\mathbf{D}$
The first coat uses half the paint, so half remains. Two thirds of this is then used so one third of one half, that is one sixth remains. So the volume remaining is $\frac{1}{6} \times 3$ litres. So there remains 0.5 litres, that is, $500 \mathrm{ml}$ of paint.