dave noticed two exits on the highway were 2.4 kilometres apart. how many metres apart were they

Each kilometre is equivalent to 1000 metres. Since there are 2.4 kilometres, a simple ratio can find the answer.

$${\mathtt{2.4}}{km}{\mathtt{\,\times\,}}\left({\frac{{\mathtt{1\,000}}{m}}{{\mathtt{1}}{km}}}\right)$$

Multiply:

$${\frac{{\mathtt{2.4}}{km}{\mathtt{\,\times\,}}{\mathtt{1\,000}}{m}}{{\mathtt{1}}{km}}}$$

The km (kilometres) cancel out and from there it is simple multiplication.

$${\frac{{\mathtt{2.4}}{\mathtt{\,\times\,}}{\mathtt{1\,000}}}{{\mathtt{1}}}} = {\mathtt{2\,400}}$$

Since there are 1000 metres in a kilometre, multiply 2.4 x 1000 to find the number of metres.