Question

Round off to $3$ significant figures,

a) $20.96$
b) $0.0003125$

• A. $21.0,312\times {10}^{-4}$
• B. $21.0,3.12\times {10}^{-4}$
• C. $2.10,3.12\times {10}^{-2}$
• D. $210,3.12\times {10}^{-4}$

Answer 1

The correct option is B $21.0,3.12\times {10}^{-4}$

$\begin{array}{c}\text{According to the rule}\\ \text{of rounding off:}\end{array}$

$\text{(a)}{20.96}^{}=21.0$

$\text{(b)}0.0003125=3.125\times {10}^{-4}=3.12\times {10}^{-4}$