Source: Extra Practice

The length and breadth of a rectangular sheet are 16.2±0.1 cm16.2 \pm 0.1\text{ cm} and 10.1±0.1 cm10.1 \pm 0.1\text{ cm} respectively. The area of the sheet in appropriate significant figures and error is:

Options

Option A

163.62 ± 2.6 cm²

Option B

163.6 ± 2.6 cm²

Option C is correct

164 ± 3 cm²

Option D

163.6 ± 3 cm²

Explanation

Area A=l×b=16.2×10.1=163.62 cm2A = l \times b = 16.2 \times 10.1 = 163.62\text{ cm}^2. Relative error ΔAA=Δll+Δbb=0.116.2+0.110.10.00617+0.00990=0.01607\frac{\Delta A}{A} = \frac{\Delta l}{l} + \frac{\Delta b}{b} = \frac{0.1}{16.2} + \frac{0.1}{10.1} \approx 0.00617 + 0.00990 = 0.01607. Absolute error ΔA=A×0.01607=163.62×0.016072.63 cm2\Delta A = A \times 0.01607 = 163.62 \times 0.01607 \approx 2.63\text{ cm}^2. Since the least significant figure in the measurements is at the tenths place and the product must follow the least significant figures of the factors (3 sig figs here), we round 163.62 to 164. The error is rounded to 3 to match the precision. Thus, 164±3164 \pm 3 is the most appropriate representation according to NCERT guidelines for propagation and rounding.