Question

A plate has a length $\left(5\pm 0.1\right)cm$ and breadth $\left(2\pm 0.01\right)cm.$ Then the area of the plate is

• A. $\left(10\pm 0.25\right)c{m}^2$
• B. $\left(10\pm 0.01\right)c{m}^2$
• C. $\left(10\pm 0.001\right)c{m}^2$
• D. $\left(10\pm 1\right)c{m}^2$

Answer 1

Answer: (A)

$\text{A}=\text{ab}$
$\frac{\Delta \text{A}}{\text{A}}=\frac{\Delta \text{a}}{\text{a}}+\frac{\Delta \text{b}}{\text{b}}$
$=\frac{\text{0.1}}{\text{5}}+\frac{\text{0.01}}{2}$
$=\frac{\text{0.2+0.05}}{10}$
$=\frac{0.25}{10}$
$\Delta \text{A}=\text{0.025}\times \text{A}$
$=\text{0.25}c{m}^2$