When performing addition and subtraction with measured values, it’s important to consider significant figures to ensure your results reflect the precision of the measurements. Here’s how you do it:
Rules for Addition and Subtraction:
- Identify the Decimal Places: First, look at the numbers you are adding or subtracting. Determine the number of decimal places in each of the values used.
- Find the Least Precise Decimal Place: Identify the measurement with the least amount of decimal places. This measurement will dictate how many decimal places your final answer can have.
- Perform the Operation: Carry out the addition or subtraction as normal.
- Round the Result: Round your final answer to the same number of decimal places as the least precise measurement you identified earlier.
Example:
Suppose you need to add 12.11 (2 decimal places) and 0.3 (1 decimal place):
- Perform the addition: 12.11 + 0.3 = 12.41
- Identify the least precise measurement: 0.3 has 1 decimal place.
- Round the result to 1 decimal place: 12.41 rounds to 12.4.
Thus, when adding 12.11 and 0.3, the result should be reported as 12.4, since that reflects the correct significant figures.