Write (a) 0.000 072 m in micrometres, (b) 3.6 Gm in kilometres, in scientific notation, (c) 480 ns…

Step 1. $0.000\,072\ \text{m} = 7.2 \times 10^{-5}\ \text{m} = \dfrac{7.2 \times 10^{-5}}{10^{-6}}\ \mu\text{m} = 72\ \mu\text{m}$.

Step 2. $3.6\ \text{Gm} = 3.6 \times 10^{9}\ \text{m} = 3.6 \times 10^{6}\ \text{km}$.

Step 3. $480\ \text{ns} = 480 \times 10^{-9}\ \text{s} = 4.8 \times 10^{-7}\ \text{s}$.