Question

If $3.8\times {10}^{-6}$ is added to $4.2\times {10}^{-5}$ giving due regard to significant figures, then the result will be

• A. $4.58\times {10}^{-5}$
• B. $4.6\times {10}^{-5}$
• C. $4.5\times {10}^{-5}$
• D. None of these

Answer 1

The correct option is B

$4.6\times {10}^{-5}$

Explanation for the correct option:

Finding the value:

By adding $3.8\times {10}^{-6}$ and $4.2\times {10}^{-5}$, we get

$4.2\times {10}^{-5}=42\times {10}^{-6}$

$\begin{array}{rcl}3.8\times {10}^{-6}+42\times {10}^{-6}& =& 45.8\times {10}^{-6}\\ & =& 4.58\times {10}^{-5}\\ & =& 4.6\times {10}^{-5}\end{array}$

$\therefore$The result is $\mathbf{4}\mathbf{.}\mathbf{6}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{5}}$

Hence, Option $\text{'}B\text{'}$ is Correct.