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Significant Figures in Calculations. Rounding . 1) Decide how many sig figs the answer should have. 2) If the digit to the right of the last digit… is less than 5, the last sig fig stays the same Example: 5241 4 4 is dropped and the answer is 5241
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Rounding • 1) Decide how many sig figs the answer should have. • 2) If the digit to the right of the last digit… • is less than 5, the last sig fig stays the same • Example: 52414 • 4 is dropped and the answer is 5241 • Is more than 5, the last value of the last sig fig increases by 1 • Example: 52416 • 1 increases to 2 and the answer is 5242
Practice • Round off each measurement to the number of sig figs shown in parentheses. Then write the answers in scientific notation. • A) 314.721 meters (four) • B) 0.001775 meter (two) • C) 8792 meters (two) • Answers: • A) 314.7 meters • 3.147 x 102 meters • B) 0.0018 meter • 1.8 x 10-3 meter • C) 8800 meters • 8.8 x 103 meters
Addition and Subtraction • Answer should be rounded to the same number of decimal places (not digits) as the measurement with the least number of decimal places. • Example: 12.52 meters + 349.0 meters + 8.24 meters • 12.52 meters + 349.0 meters + 8.24 meters 369.76 meters (has to be rounded to the tenths place) • Final answer: 369.8 meters
Practice • Perform each operation. Express your answers to the correct number of sig figs: • A) 61.2 m + 9.35 m + 8.6 m • B) 9.44 m – 2.11 m • C) 1.36 m + 10.17 m • D) 34.61 m – 17.3 m • Answers: • A) 79.2 m • B) 7.33 m • C) 11.53 m • D) 17.3 m
Multiplying and Dividing • Round the answer to the same number of significant figures as the measurement with the least amount of sig figs
Practice • Perform the following operations. Give the answers to the correct number of sig figs. • A) 7.55 m x 0.34 m • B) 2.10 m x 0.70 m • C) 2.4526 m ÷ 8.4 • Answers: • A) 2.6 meters2 • B) 1.5 meters2 • C) 0.29 meter