SIGNIFICANT DIGITS RULES FOR SIGNIFICANT DIGITS 1. Non-zero digits are ALWAYS significant. Example- 123456789 2. Zeros that are between other significant digits are ALWAYS significant. Example- 3004 3. Final zeros that occur before or after the decimal are ALWAYS significant. Example- 78.00 4. Zeros used for spacing the decimal are NOT significant. Example- 0.003 EXAMPLES 3 SIG FIGS 4 SIG FIGS 5 SIG FIGS 250 m/s 3150 m/s 74850 m/s 25.0 m/s 315.0 m/s 7485.0 m/s 2.50 m/s 31.50 m/s 748.50 m/s 0.250 ml 3.150 ml 74.850 ml 0.0250 ml 0.3150 ml 7.4850 ml 0.00250 ml 0.03150 ml 0.74850 ml 0.000250 ml 0.003150 ml 0.074850 ml 700 m/s 7 000 m/s 70 000 m/s 8.07 x 106 m/s 8.007 x 106 m/s 8.0007 x 106 m/s HOW MANY SIGNIFICANT DIGITS? 2804 2.84 0.0029 4.6 X 104 75.00 50000 360 0.00305 30.24 6.89 0.001 6.0 123.056 100.04 ADDING & SUBTRACTING When you have numbers to add/subtract you will sometimes need your answer to have the correct number of significant digits. Here is the rule: Look at all of the numbers to add/subtract and find the number with the LEAST number of sig. digs. AFTER the decimal. This is how many sig. digs. should be after the decimal in your answer. Example 24.686 2.343 3.21 30.239 ANSWER = 30.24 MULTIPLYING & DIVIDING When you have numbers to multiply/divide you will sometimes need your answer to have the correct number of significant digits. Here is the rule: Look at all of the numbers to multiply/divide and find the number with the LEAST number of sig. digs. This is how many sig. digs. that you should have in your answer. Example - 3.22 x 2.1 = 6.762 ANSWER = 6.8 EXAMPLE PROBLEMS FOR +/• 1.2 + 1.26 = • 2.46 • • 2.476-1.72 = • 0.756 • • Final Answer: 2.5 Final Answer: 0.76 10.72694321 – 10.1 = • 0.62694321 • Final Answer: 0.6 EXAMPLE PROBLEMS FOR X/÷ • 1.53 x 2.5 • 3.825 • • 10.0 / 5.0 = • 2 • • Final Answer: 3.8 Final Answer: 2.0 10.2 x 1000 • 102,000 • Final Answer: 10.2 x 10³