Question:
The thickness of a plate is measured to be $2.17 \mathrm{~mm}, 2.17 \mathrm{~mm}$ and $2.18 \mathrm{~mm}$ at three different places. Find the average thickness of the plate from this data.
Solution:
Average thickness
$=\frac{2.17+2.17+2.18}{3}=2.1733 \mathrm{~mm}$
Now we have to round it off to three significant figures. So, after 7 , the digit is 3 . Hence, Average thickness $=2.17 \mathrm{~mm}$.