Question

A person was weighting 102.1 kg last week and gained 0.28 kg this week. His weight as of now is correctly expressed as:

• A. 102.38 kg
• B. 102.3 kg
• C. 102.4 kg
• D. 102 kg

Answer 1

Answer: (C)

102.4 kg

Answer 2

In addition or subtraction, the last significant digit of the sum or difference occupies the same relative position as the last significant digit of the quantities being added or subtracted. In the result there should only be one uncertain digit. Also sum of a certain and a uncertain digit becomes uncertain.

As there can only be one uncertain digit in the result, therefore 3 which comes by addition of certain digit 2 and uncertain digit 1, is rounded off to 4. It is kept as the uncertain digit.

After round off $= \underbrace { 102.4 } \longleftrightarrow$ Uncertain digit