8-2

1. 8-2 Accuracy and Precision Course 2 Warm Up Problem of the Day e e e e Lesson Presentation

2. 8-2 Accuracy and Precision Course 2 Warm Up Convert. 1.216 hr = ____ days 2. 3.7 kg = ____ g 3. 4.5 qt = ____ pt 4. 7.2 mm = ____ cm 9 3700 9 0.72

3. 8-2 Accuracy and Precision Course 2 Problem of the Day Polly found that an empty bird cage weighs 18 oz. With a bird in it, the cage weighs 24 oz. Polly calculated the bird must weigh 6 oz. How far off might that calculation be? 1 oz in either direction; each weight might be off 0.5 oz in either direction.

4. 8-2 Accuracy and Precision Course 2 Learn to compare the precision of measurements and to determine acceptable levels of accuracy.

5. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Vocabulary precision accuracy significant digits

6. 8-2 Accuracy and Precision Course 2 Ancient Greeks used measurements taken during lunar eclipses to determine that the Moon was 240,000 miles from the Earth. In 1969, the distance was measured as 221,463 miles. There is a difference between these measurements because modern scientists conducted the measurement with greater precision. Precision is the level of detail an instrument can measure.

7. 8-2 Accuracy and Precision Course 2 The smaller the unit an instrument can measure, the more precise its measurements will be. For example, a millimeter ruler has greater precision than a centimeter ruler because it can measure smaller units.

8. 8-2 Accuracy and Precision Course 2 Additional Example 1A &1B: Judging Precision of Measurements Choose the more precise measurement in each pair. A. 13 oz, 1 lb Since an ounce is a smaller unit than a pound, 13 oz is more precise. B. 52 cm, 52.3 cm Since 52.3 has the smaller decimal place, 52.3 cm is more precise.

9. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Try This: Example 1A &1B Choose the more precise measurement in each pair. A. 1 gal, 5 qt Since a quart is a smaller unit than a gallon, 5 quarts is more precise. B. 5.4 mi, 15,000 m Since a meter is a smaller unit than a mile, 15,000 meters is more precise.

10. 8-2 Accuracy and Precision Course 2 In the real world, no measurement is exact. The relative exactness of a measurement is its accuracy. In a measured value, all the digits that are known to be exact are called significant digits. Zeros at the end of a whole number are assumed to be nonsignificant.

11. 8-2 Accuracy and Precision Course 2 The table shows the rules for identifying significant digits. 3 significant digits • Nonzero digits 45.7 • Zeros between significant digits 5 significant digits 78,002 • Zeros after the last nonzero digit and to the right of a decimal point 2 significant digits 0.0040

12. 8-2 Accuracy and Precision Course 2 Additional Example 2A & 2B: Identifying Significant Digits Determine the number of significant digits in each measurement. A. 304.7 km The digits 3, 4, and 7 are nonzero digits, and 0 is between two nonzero digits. So 304.7 has 4 significant digits. B. 0.0760 L The digits 7 and 6 are nonzero digits, and 0 is to the right of the decimal after the last nonzero digit. So 0.0760 L has 3 significant digits.

13. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Try This: Example 2A & 2B Determine the number of significant digits in each measurement. A. 230.4 mi The digits 2, 3, and 4 are nonzero digits, and 0 is between two nonzero digits. So 230.4 mi has 4 significant digits. B. 0.0460 kg The digits 4 and 6 are nonzero digits, and the 0 is to the right of the decimal after the last nonzero digit. So 0.0460 kg has 3 significant digits.

14. 8-2 Accuracy and Precision Course 2 When you are adding and subtracting measurements, the answer should have the same number of digits to the right of the decimal point as the measurement with the least number of digits to the right of the decimal point.

15. 8-2 Accuracy and Precision Course 2 Additional Example 3: Using Significant Digits in Addition or Subtraction Calculate 67 ft – 0.8 ft. Use the correct number of significant digits in the answer. 67 – 0.8 0 digits to the right of the decimal point 1 digit to the right of the decimal point 66.2  66 ft Round the difference so it has no digits to the right of the decimal point.

16. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Try This: Example 3 Calculate 15 ft – 3.8 ft. Use the correct number of significant digits in the answer. 0 digits to the right of the decimal point. 15 – 3.8 1 digit to the right of the decimal point. 11.2  11 ft Round the difference so it has no digits to the right of the decimal point.

17. 8-2 Accuracy and Precision Course 2 When you are multiplying and dividing measurements, the answer must have the same number of significant digits as the measurement with the least number of significant digits.

18. 8-2 Accuracy and Precision Course 2 Additional Example 4: Using Significant Digits in Multiplication or Division Calculate 19.8 mm · 1.4 mm. Use the correct number of significant digits in the answer. 19.8 3 significant digits.  1.4 2 significant digits 27.72 28 mm Round the product so that it has 2 significant digits. 

19. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Try This: Example 4 Calculate 2.43 m · 31 m. Use the correct number of digits in the answer. 2.43 3 significant digits.  31 2 significant digits. 75.33 75 m  Round the product so that it has two significant digits.

20. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Lesson Quiz: Part 1 1.Which measurement is more precise, 10 in. or 1 ft? Determine the number of significant digits in each measurement. 2. 6.004 3. 0.070 Calculate. Give the answer with the correct number of significant digits. 4. 72 – 0.8 5. 18.3 · 4.1 10 in. 4 2 71 75

21. 8-2 Accuracy and Precision Course 2 Insert Lesson Title Here Lesson Quiz: Part 2 6. A veterinarian’s assistant finds that a dog weighs 11 kg. What is the least and the most the dog might really weigh? 10.5 kg to 11.5 kg