#26
Describe the rules that are used to determine the number of significant figures in the results of addition/subtraction and multiplication/division.
When multiplying or dividing, the answer should be rounded to contain the same number of significant figures as the least accurate number.
0.300 (3 s.f.) x 405.7009 (7 s.f.) = 3 s.f. in answer
5000. (4 s.f.) / 10.32 x 10^-10 (4 s.f.) = 4 s.f. in answer
When adding or subtracting, the answer should have the same number of decimal places as the least accurate number used in the calculation.
84 + 87,600 + 9.005 = round answer to the nearest whole number
10.00405 - 5,400.5 + 6.32 = round answer to nearest tenth
Great job Mercedez, I would just add a few more examples to your answer and add more to your definition so people really understand.
ReplyDeleteIn addition or subtraction, the uncertainty is determined by the absolute uncertainty in the least precise measurement (not by the number of significant figures).
Example
32.01 m
5.325 m
12 m
Whenn added the sum is49.335 m, but the sum should be '49' meters.
When mutiplied or divided, the number of significant figures in the result is the same as that in the quantity with the smallest number of significant figures. If, for example, a density calculation is made in which 25.624 grams is divided by 25 mL, the density should be reported as 1.0 g/mL, not as 1.0000 g/mL or 1.000 g/mL.
http://chemistry.about.com/od/mathsciencefundamentals/a/sigfigures.htm
Good job Mercedez. Your explanations are great I would just add answers to your examples so people can understand the number of sig figs.
ReplyDelete0.300 (3 s.f.) x 405.7009 (7 s.f.) = 122
5000. (4 s.f.) / 10.32 x 10^-10 (4 s.f.) = 4.845
84 + 87,600 + 9.005 = 88,000
10.00405 - 5,400.5 + 6.32 = -5384.2
Great Job Mercedez. Your explanations for multiplication and division, and addition and subtraction are very good, but another important rule about sig figs are exact values. When given an exact value, such as counted values or defined quantities, they have unlimited sig figs. For example, if a problem were to say there were 12 pencils in a bag, or 24 students in a class, this would not have two sig figs, but unlimited sig figs because it is a counted value. Another example would be 1 foot = 12 inches. This is a defined value since there are exactly 12 inches in a foot. None of these exact numbers affect the answer to the problem because they all have an unlimited number of sig figs.
ReplyDelete