Significant Figures Part 2
Problem Solving Applications
Multiplying & Dividing
• When multiplying or dividing, your
answer may only show as many
significant digits as the multiplied or
divided measurement showing the least
number of significant digits.
Examples
• 22.37 cm x 3.10 cm x 85.75 cm
= 5946.50525 cm3
= 5950 cm3
• (3.0 x 105 m2)/(2.45 x 103 m)
= 122.4489…m
= 120 m
More Examples
• 5000 g / 4.25 g
= 1176.470588
= 1000
• 2500 N x 40. N
= 100000 N2
= 1.0 x 105 N2
Adding and Subtracting
• When measured quantities are used in
addition or subtraction, the uncertainty
is determined by the absolute
uncertainty in the least precise
measurement (not by the number of
significant figures). Sometimes this is
considered to be the number of digits
after the decimal point.
Examples
• 3.45 cm + 8.1 cm = 11.55 cm
= 11.6 cm
• 31.492 g – 30.9481 g = .5439 g
= .544 g
• 685 N + 3.9 N = 688.9 N
= 689 N
More Examples
• 1060 L – 997.2 L = 62.8 L
= 60 L
• 890 Kg + 0.874 Kg = 890.874 Kg
= 890 Kg
Practice Problems
1.
2.
3.
4.
890 / 5.86 = 151.8771331 = 150
8.203 x 4.3 = 35.2729 = 35
300 x 52 = 15600 = 20000
40. x (6.02 x 1023) = 2.408 x 1025 = 2.4 x
1025
5. (3.50 x 102) / (8.2 x 103) = 0.0426829268
= 0.043 or 4.3 x 10-2
Practice Problems
6. 6. 3.00 + 82.890 + 4.8 = 90.69 = 90.7
7. 7. 3.24 – 1.005 – 0.023 = 2.212 = 2.21
8. 81.02 + 25 – 8.023 = 17.997 = 18
9. 30 – 5.9 + 2.45 = 26.55 = 30
10.56.8 + 20. – 42.33 = 34.47 = 34