The length and breadth of a metal sheet are 3.124 m and 3.002 m respectively, the area of this sheet up to four correct significant figure is 

According to rule of significant figures.

1. Any zeros that are between non-zeros are also considered significant
2.  All non-zero digits are significant

Hence, breadth of metal b = 3.002 m has four significant figures.

$\therefore$Length of metal = 3.124 m has four significant figures.

Since length and breadth have four significant,

Therefore

$\mathrm{Area}=\mathrm{length}\times \mathrm{breadth}$

= $3.124\times 3.002=9.378248$

Will also have four significant figures.

Hence, area = $9.378{\mathrm{m}}^2$

Errors of measurement.