Q 11-01-049NEETJEE MainMedium
The length and breadth of a rectangular sheet are $(12.0 \pm 0.1)\ \text{cm}$ and $(5.0 \pm 0.1)\ \text{cm}$. Its area, with the error limit, is
Answer: (B) $(60 \pm 1.7)\ \text{cm}^2$
$A = 12.0\times 5.0 = 60\ \text{cm}^2$
For a product, the fractional errors add:
$$\frac{\Delta A}{A} = \frac{0.1}{12.0} + \frac{0.1}{5.0} = 0.0083 + 0.020 = 0.0283$$
$$\Delta A = 0.0283\times 60 \approx 1.7\ \text{cm}^2$$
So $A = (60 \pm 1.7)\ \text{cm}^2$.
Solution by Sreeraj P, M.Sc Physics