### Theory:

We can use decimals to measure the length of the object.

Kilometre$$(km)$$, Metre$$(m)$$, Centimetre$$(cm)$$ and Millimetre$$(mm)$$ are the measurements used to measure length.
$\begin{array}{l}1\phantom{\rule{0.147em}{0ex}}m=\frac{1}{1000}\phantom{\rule{0.147em}{0ex}}\mathit{km}=0.001\phantom{\rule{0.147em}{0ex}}\mathit{km}\\ \\ 1\phantom{\rule{0.147em}{0ex}}\mathit{cm}=\frac{1}{100}\phantom{\rule{0.147em}{0ex}}m=0.01\phantom{\rule{0.147em}{0ex}}m\\ \\ 1\phantom{\rule{0.147em}{0ex}}\mathit{mm}=\frac{1}{10}\phantom{\rule{0.147em}{0ex}}\mathit{cm}=0.1\phantom{\rule{0.147em}{0ex}}\mathit{cm}\end{array}$
Example:
1. Convert $$7$$ $$m$$ to $$km$$.

$\begin{array}{l}1\phantom{\rule{0.147em}{0ex}}m=\frac{1}{1000}\phantom{\rule{0.147em}{0ex}}\mathit{km}\\ \\ 7\phantom{\rule{0.147em}{0ex}}m=\frac{7}{1000}\phantom{\rule{0.147em}{0ex}}\mathit{km}=0.007\phantom{\rule{0.147em}{0ex}}\mathit{km}\end{array}$

Therefore, $$7$$ $$m$$ $$=$$ $$0.007$$ $$km$$.

2. Convert $$56$$ $$mm$$ to $$cm$$

$\begin{array}{l}1\phantom{\rule{0.147em}{0ex}}\mathit{mm}\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}\frac{1}{10}\phantom{\rule{0.147em}{0ex}}\mathit{cm}\\ \\ 56\phantom{\rule{0.147em}{0ex}}\mathit{mm}\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}\frac{56}{10}\phantom{\rule{0.147em}{0ex}}\mathit{cm}\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}5.6\phantom{\rule{0.147em}{0ex}}\mathit{cm}\end{array}$

Therefore, $$56$$ $$mm$$ $$=$$ $$5.6$$ $$cm$$.