10. During a rainstorm, 15 litres of water fell per square metre. By how much did the water level in Michael's outdoor pool rise?
10. D One litre is equivalent to $1000 \mathrm{~cm}^{3}$. Hence 15 litres falling over an area of one square metre is equivalent to $15000 \mathrm{~cm}^{3}$ falling over an area of $10000 \mathrm{~cm}^{2}$. Therefore the amount the water in Michael's pool would rise by, in $\mathrm{cm}$, is $15000 \div$ $10000=1.5$.