Question

Two numbers are given as i) 20.96 and ii) 0.0003125. Rounding off above numbers to 3 significant figures will lead to :

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

Answer 1

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

a) 20.96
We have to round off for 3 significant digits. Last digit has to be rounded off.
If the digit to be dropped (6) is more than 5, then preceding digit is raised by 1.
Hence $20.96\approx 21.0$

b) $0.0003125=3.125\times {10}^{-4}$
For 3 significant digits $\Rightarrow 3.12\times {10}^{-4}$