Knowing Our Numbers — MATHS STD 6 — Question

We know that, $1$ centimeter $= 10\ mm, 1$ meter $= 100\ cm\ 1$ meter $= 1000$
mm or $1\ mm =\frac{1}{10}\text{cm} \text { or}1\text{ mm}=\frac{1}{1000}\text{m}$
To convert $4000\ mm\ 400\ cm$ to meters
$4000\ mm \ 400\ cm = 4000\ mm + 400\ cm$
Now, $4000\ mm =\frac{1}{1000}\times{4000}\text{m}=4\text{m }{ 400}\text{cm}=\frac{1}{100}\times{400}\text{m} =4\text{m}$
$4000\ mm\ 400\ cm = 4000\ mm + 400 \ cm = (4+4)\ m = 8\ m$