Why are Significant Figures important?...
Well, they help make the number more precise. Numbers which have more significant digits are more precise. The last number in the measurement are usually uncertain.
There are some rules that are associated with making significant figures as precise as possible.
Rules on how to count the number of significant figures:
1) All number's that are not zero are always SIGNIFCANT
ex. 35322 , this number has 5 significant digits
2) Zeros that are in front of the non-zero numbers are NOT SIGNIFICANT
ex. 0.0065 , this number has 2 significant digits
3) Zero's that come after a decimal point ARE COUNTED
ex. 50.601 , this number has 5 significant digits
4) Zero's that come after numbers, but are NOT after a decimal point, are NOT COUNTED
ex. 340000000 , this number only has 2 significant digits
Both Number's have 2 Significant Figures
Some numbers require rounding, however, there are "exact numbers" that require no rounding at all. For example, you cannot say that there are 2.4 numbers of deers. Or say that there are 5.6 jackets.
So now that you know how to count significant numbers, let's learn how to round!!
Here are some rules for rounding:
1) Always look at the number to the right of the digit you want to round
2) If the digit is greater than 5, round up, and if the digit is less than 5,the number stays the same.
3)If the digit is the number 5, and there are more non-zero digits after the 5, round up
4)If that digit ends in the number 5, round the digit to make it an even number, (0,2,4,6,8)
In addition to rounding rules, there are also math rules.
When you add or subtract, remember to round to the number that has the fewest number of decimal places. You determine this by the number's position.
For example,
11.34 L
+ 13.4 L
___________
___________
24.74 L ----> 24.7 L
For this equation, you round to the nearest tenth, because that number has the fewest number of decimal places.
Multiplying and Dividing is a bit different from adding and subtracting significant digits. When you multiply and divide you round to the fewest number of significant digits.
For example,
12.3 Km
x1.2 Km
_______
14.76Km ----> 14.8Km
For this equation, the number with the fewest number of significant digits is 1.2, which has 2 significant figures. So the new number has to have only two significant figures too.
ANDDD... THAT IS ALL :)
But... for more practice, visit this site:
Also, watch this funnish video to reinforce your understanding:
im cool... like the wind
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