Significant figures The number of digits which describe a measurement

Measurements

Rules for significant figures All nonzero numbers are significant All zeros between significant digits are significant All numbers BOTH after a significant digit AND after a DECIMAL are significant. Placeholders are never significant 1, 2, 3, 4….. 9 ex: = five significant figures ex: = five significant figures ex: = five significant figures ex: = two significant figures

Your turn

Counting numbers – have infinite significant figures, as do conversion facctors which are definitions km is EXACTLY 1/ cm is exactly basketballs cannot be 3.1 basketballs.

Rules for adding Anything which lines up can be added = still equals 300 because 200 has only one significant digit, so the zero is being added to an unknown number. (200 could be 160 or it could be 240 because it only has one significant digit.) = 3.22 because there is nothing in the 1/1000 place of the 1.00 so we don’t know SHOULD be there could be or it could be and would still be written as We don’t know what the tens’ place really is!

Rules for subtracting Anything which lines up can be subtracted = still equals 100 because 200 has only one significant digit, So we don’t know if it is 200 or 210 or 220 or even = 1.88 because there is nothing in the 1/1000 place of 3.00 so we don’t know SHOULD be there.

Rules for multiplication and division Whichever number has the fewest significant digits determines the number of significant digits in the answer x 2.0 = 22.2, but it must be rounded to 22 because 2.0 has only two significant digits x 2.00 = , but it must be rounded to 22.2 because 2.00 has only three significant digits /1.0 = 33 because 1.0 has only two significant figures.