If the length and breadth of a thin rectangular sheet are measured, using a metre scale as 16.2 cm and 10.1 cm respectively. What is the area of the rectangular sheet. 

Explanation

There are three significant figures in each measurement. It means that the length l may be written as `l= 16.2 +- 0.1cm= 16.2 cm +- 0.6%` Similarly, the breadth b may be written as `b= 10.2 +- 0.1cm= 10.1 cm +- 1%`
Then, the error of the product of two (or more) experimental values, using the combination of errors rule, will be
`lb= 163.62 cm^(2) +- 1.6% - 163.62 +- 2.6cm^(2)`
This leads use to quote the final result as `lb= 164 +- 3 cm^(2)`
Here `3cm^(2)` is the uncertainty or error in the estimation of area of rectangular sheet.