Question

The length and breadth of a field are measured as: $l=(120\pm 2)m$ and $b=(100\pm 5)m$, respectively. What is the area of the field?

Answer 1

Now $\frac{△A}{A}=\frac{△l}{l}\frac{△b}{b}=(\frac{2}{120}+\frac{5}{100})=0.0667$;
$△A=0.0667\times A$
Now $A=l.b=120\times 100=12000m^2$
$\Rightarrow △A=0.0667\times 12000=800.4m^2$
Area of the field = $A\pm △A$$=12000\pm 800.4=(1.2\pm 0.08)\times {10}^4{m}^2$