Significant Figures
Rules:
 #1 – Nonzero digits are significant
 19
 311
 7862
 1,237,983
 #2 – Zeros between significant figures are significant
 109
 5002
 6507
 1,000,341
Rules
 #3 – Final zeros after a decimal are significant
 10.0
 234.00
 2986.000
 10000.00
 #4 – Zeros that are placeholders are NOT significant
 10
 0.0003
 350,000
 0.099
Rounding
 When rounding to a specific amount of significant figures:
 In scientific notation, all numbers preceding “x10” are significant
 5-9 as next digit: round up
 1-4 as next digit: round down
 If you end up with zeros that need to be significant, but are not:
 Add a decimal at the end of the number

All previous digits are then significant

100 rounded to 3 significant digits = 100.
 Add a bar over the final significant zero

100 rounded to 2 significant digits = 100
The Quick Method:
 If there is a decimal, count all digits to the right of the first
nonzero digit as significant.
 0.00150
 0.0005
 10.010
 10,120.0
 If there is NOT a decimal, count all digits to the left of the first
nonzero digit.
 10,000
 230,450
 250
 1,205,375,000