Question

100 millimetres is how many centimetres?

Answer 1

Prefixes are used to denote large or small quantities with ease.
centi is equivalent to 0.01
milli is equiavlent to 0.001

Hence,
$1cm=0.01m$
$1mm=0.001m$

$⟹10mm=1cm$
$\therefore 100mm=10cm$