Question

Subtract $2.5\times {10}^4$ from $3.9\times {10}^5$ and give the answer to correct number of significant figures.

• A. $3.6\times {10}^6$
• B. $3.6\times {10}^5$
• C. $36\times {10}^5$
• D. $36\times {10}^6$

Answer 1

The correct option is B $3.6\times {10}^5$

We have $3.9\times {10}^5-2.5\times {10}^4$

$=3.9\times {10}^5-0.25\times {10}^5$

$=3.65\times {10}^5$

But our answer should be rounded off upto two significant digits.

So the ans is $3.6\times {10}^5$