Express as centimeter(cm) using decimal 4cm5mm.

Hint: This is a very simple question of unit conversion. We know that 1cm = 10mm, and we also know that we can express any unit which is the combination of more than two units of the same quantity as the sum of the number of different units which are present in the given unit. Suppose, we are given a rod whose length is equal to$a\operatorname{cm}b\operatorname{mm}$, then, we can write it as:\[a\operatorname{cm}b\operatorname{mm}=a\operatorname{cm}+b\operatorname{mm}\], and then apply unit conversion and convert it into the required unit of that quantity.

Complete step by step answer:
We know that from the question that we have to convert the unit into the required unit. And, 4cm5mm is also a combination of two units (i.e. cm and mm) and both of the units are used to measure length and we have to convert both into the same unit, i.e. cm.
So, we can write 4cm5mm by splitting it into addition of two terms as:
4cm5mm = 4cm + 5mm……………… (1)
Now, we also know that 1cm = 10 mm.
Then, we can write \[1\operatorname{mm}=\dfrac{1}{10}\operatorname{cm}\]:
So, multiply 5mm of equation (1) by $\dfrac{1}{10}$to convert it into cm.
$\Rightarrow 4\operatorname{cm}5\operatorname{mm}=4\operatorname{cm}+5\times \dfrac{1}{10}\operatorname{cm}$
\[=4\operatorname{cm}+0.5\operatorname{cm}\]
$=4.5\operatorname{cm}$

Note: While we are converting units, we do a lot of calculation so we should avoid calculation mistakes and we are also required to know all the possible relationships among the units of the same quantity and should not confuse among their relationships.