Do you add first or round first?
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The first step in estimating a sum or a difference is to round the numbers, by changing them to the nearest power of ten, hundred, thousand, etc. Round the numbers first, then use mental math to estimate an answer. When rounding, follow these rounding rules: If the number being rounded is less than 5, round down.
Keeping this in view, do you round before or after adding?
As you can see, in finding a round sum, it is quickest to round the numbers before adding them. 1. Some statisticians prefer to round 5 to the nearest even number. As a result, about half of the time 5 will be rounded up, and about half of the time it will be rounded down.
Accordingly, what is the Sigfig rule for addition?
Your answer cannot be MORE precise than the least precise measurement. For addition and subtraction, look at the decimal portion (i.e., to the right of the decimal point) of the numbers ONLY. 1) Count the number of significant figures in the decimal portion of each number in the problem.
Scientific Notation
(1) | 1000 | 1x103 -- so one sig fig |
---|---|---|
(2) | 0.001 | 1x10-3 -- so one sig fig |
(3) | 100. | 1.00x102 -- so three sig figs |
(4) | 0.00100 | 1.00x10-3 -- so three sig figs |
(5) | 100 (with two sig figs) | 1.0x102 -- so two sig figs |