How do you know how many sig figs to round to?

Answer 1

Determining Number of Significant Figures (Sig Figs)

1.All non-zero numbers are significant. 6924 has four sig figs.

2.Leading zeros are not significant. 0.0003679 has four sig figs.

3.Zeros between other significant figures are significant. 0.00041092 has five sig figs.

4.Trailing zeros are significant if there is a decimal. 0.046802000 has eight sig figs.

Multiplication and Division

Round the answer to the same number of significant figures (sig figs) as the measurement with the fewest sig figs in the problem.

34.9cm x 4.7cm = 164.03cm2 = 160cm2 (rounded to two sig figs)

271.0g/99.8cm3 = 2.71543g/cm3 = 2.715 (rounded to four sig figs)

Addition and Subtraction

Round the answer to the fewest decimal places as the measurement with the fewest decimal places.

9.45kg + 8.329kg = 17.78kg (rounded to two decimal places)

Rounding Rules:

If the number to be dropped is less than four, keep the number in front the same. 3.43 would be rounded to 3.4 .

If the number to be dropped is greater than five, round the number in front up by 1. 3.46 would be rounded to 3.5 .

If the number to be dropped is exactly five, keep the number in front the same if it is even. If the number in front is odd, round up by 1.

4.65 rounds to 4.6 .

4.75 rounds to 4.8 .