1. Uncertainty of 2500 mL: hundreds place [Larger]
QUESTION:
To how many significant figures should the result of the following calculation be reported? mL + 25 mL A. 2, B. 3, C. 4, D. 5
Rule for addition or subtraction: last sigfig location in the answer is same as in the term with the larger uncertainty. Location of last sigfig implies magnitude of uncertainty
Uncertainty of 2500 mL: hundreds place [Larger]
Uncertainty of 25 mL: ones place
Therefore: last sigfig in answer is in hundreds place mL  mL, or 2.5x103 mL
SCRIPT 1A-4-4
To how many significant figures should the result of the following calculation be reported?
Two thousand five hundred milliliters
Plus
Twenty five milliliters.
CLICK
When adding or subtracting numbers, the location of the last significant digit in the answer must be the same as that in the term with the larger uncertainty.
Let’s examine the terms that we’re adding here.
The last significant digit in two thousand five hundred milliliters is in the hundreds place. Remember than trailing zeros in a number with no decimal point are not significant.
HIGHLIGHT 5 in 2500
This means that the magnitude of the uncertainty in 2500 milliliters is in the hundreds place.
For twenty five milliliters, the last significant digit is in the ones place. HIGHLIGHT 5 in 25.
This means that the magnitude of the uncertainty in 25 grams is in the ones place.
Since the hundreds place is larger than the ones place., the last significant figure in the answer should be in the hundreds place. The answer should be reported to the nearest hundred. HIGHLIGHT 2500 mL , or 2.5x103 mL
The last significant digit in the answer is the 5 in the hundreds place.
Therefore, the correct answer is 2. The answer should be reported to two significant figures. HIGHLIGHT 25 in 2500 mL, and 2.5 in 2.5x103 mL
If you find it disconcerting that result of adding 25 to 2500 is still 2500… think of this way…
The way 2500 mL is written, it is implied that the uncertainty is at least 100 mL.
Twenty five mL is significantly less than 100 mL.
PAUSE 2 seconds
END RECORDING

2. Video ID: 1A-4-4 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08