A cuboidal tank with a base 4 m by 2.5 m holds 15,000 litres when completely full. Find the depth of the tank. (1000 L = $1{\text{m}}^3$)

15,000 L = $15{\text{m}}^3$. Base area = $4\times 2.5=10{\text{m}}^2$. Depth = 15 ÷ 10 = 1.5 $m$. Trap 15 $m$: converting 15,000 L to $150{\text{m}}^3$ (dividing by 100 instead of 1000). Trap 0.15 $m$: dividing by 1000 a second time. Trap 1500 $m$: skipping the litre-to-$m^3$ conversion altogether.