NEET 2020 Physics Question 176 Solution

For addition and subtraction of experimental measurements: 'The final result should retain as many decimal places as there are in the number with the least decimal places.'

- In $$9.99\text{ m}$$, there are 2 digits after the decimal point. - In $$0.0099\text{ m}$$, there are 4 digits after the decimal point. The result must therefore be restricted to 2 decimal places.

$$9.9900 - 0.0099 = 9.9801\text{ m}$$.

Looking at the third decimal digit in $$9.9801$$: it is $$0$$ ($$< 5$$), so the preceding digit ($$8$$) remains unaltered. Rounded result = $$9.98\text{ m}$$. Matches Option 2.