Significant Figures Practice

Rule 1 for Identifying Significant Figures

All non-zero digits are significant.

Rule 2 for Identifying Significant Figures

All trapped zeros are significant.

Rule 3 for Identifying Significant Figures

If a decimal point is present, all final zeros are significant.

Rule 4 for Identifying Significant Figures

Zeros before a number are never significant.

Rule 1 for Rounding Significant Figures

Round everything normally unless the digit to the right of the last significant digit is a 5.

Rule 2 for Rounding Significant Figures

If the digit to the right of the last significant figure is a 5 followed by non-zero digits, round up.

Rule 3 for Rounding Significant Figures

If the digit to the right of the last significant figure is a 5 followed by a 0 or nothing, look at the last significant figure. If it's even keep it the same; if it's odd, round up.

Rule for Adding or Subtracting Significant Figures

Round answers to the least precise decimal place in the original measurements.

Rule for Multiplying or Dividing Significant Figures

Round the answer to the same number of significant figures as the original measurement with the fewest significant figures.

How many sig figs are in 2804 m?

4

How many sig figs are in 0.003068 m?

4

How many sig figs are in 750 m?

2

How many sig figs are in 75.00 m?

4

How many sig figs are in 2.84 km?

3

How many sig figs are in 4.6 x 10⁵ m?

2

How many sig figs are in 75 m?

2

How many sig figs are in 75,000.0 m?

6

How many sig figs are in 75,000 m?

2

How many sig figs are in 10 cm?

1

Round 3.682417 to four sig figs.

3.682

Round 21.860051 to four sig figs.

21.86

Round 375.6523 to four sig figs.

375.7

Round 375.6523 to three sig figs.

376

Round 45.4673 to three sig figs.

45.5

Round 5.687524 to one place after the decimal.

5.7

Round 7.555 to one place after the decimal.

7.6

Round 7.455 to one place after the decimal.

7.5

Round 7.450 to one place after the decimal.

7.4

Round 7.350 to one place after the decimal.

7.4

6.201 cm + 7.4 cm + 0.68 cm +12.0 cm =

26.3 cm

1.6 km + 1.62 m +1200 cm =

1600 m (change everything to meters first, then add)

1.6 km + 1.62 m +1200. cm =

1603 m (change everything to meters first, then add)

8.264 g - 7.8 g =

0.5 g

10.4168 m - 6.0 m =

4.4 m

12.00 g +15.001 kg=

15.013 kg (change g to kg first, then add)

1.31 cm x 2.3 cm =

3.0 cm²

5.7621 m x 6.201 m =

35.73 m²

20.2 cm / 7.41 s =

2.73 cm/s

40.002 g / 13.000005 g = 3.0771

3.0771 (units cancel out)

When do we use significant figures?

for measured values only