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Scientific Notation Warm Up Order each set of numbers from least to greatest. 1. 10 4, 10 –2, 100 , 10 –1 10–2, 10–1, 100, 104 2. 82, 8–2, 83 , 80 8–2, 80, 82, 83 3. 23 , 2–6 , 2–4, 21 2–6, 2–4, 21 , 23 4. 5.22, 5.29 , 5.2–1 , 5.2–2 5.2–2, 5.2–1, 5.22, 5.29 Learn to express large and small numbers in scientific notation. Vocabulary scientific notation An ordinary penny contains about 20,000,000,000,000,000,000,000 atoms. The average size of an atom is about 0.00000003 centimeters across. The length of these numbers in standard notation makes them awkward to work with. Scientific notation is a shorthand way of writing such numbers. In scientific notation the number of atoms in a penny is 2.0 1022, and the size of each atom is 3.0 10–8 centimeters across. Helpful Hint The sign of the exponent tells which direction to move the decimal. A positive exponent means move the decimal to the right, and a negative exponent means move the decimal to the left. Example: Translating Scientific Notation to Standard Notation Write the number in standard notation. A. 1.35 105 1.35 10 5 105 = 100,000 1.35 100,000 135,000 Think: Move the decimal right 5 places. Example: Translating Scientific Notation to Standard Notation Continued Write the number in standard notation. B. 2.7 10 –3 –3 1 2.7 10 10 –3 = 1 100 2.7 100 2.7 100 Divide by the reciprocal. 0.0027 Think: Move the decimal left 3 places. Example: Translating Scientific Notation to Standard Notation Continued Write the number in standard notation. C. –2.01 104 4 –2.01 10 10 4 = 10,000 –2.01 10,000 –20,100 Think: Move the decimal right 4 places. Try This Write the number in standard notation. A. 2.87 109 2.87 10 9 10 9 = 1,000,000,000 2.87 1,000,000,000 2,870,000,000 Think: Move the decimal right 9 places. Try This Write the number in standard notation. B. 1.9 10–5 –5 1 1.9 10 –5 10 = 10,000 1 1.9 10,000 1.9 10,000 Divide by the reciprocal. 0.000019 Think: Move the decimal left 5 places. Try This Write the number in standard notation. C. –5.09 108 –5.09 10 8 10 8 = 100,000,000 –5.09 100,000,000 –509,000,000 Think: Move the decimal right 8 places. Example: Translating Standard Notation to Scientific Notation Write 0.00709 in scientific notation. 0.00709 Move the decimal to get a number 7.09 between 1 and 10. 7.09 10 Set up scientific notation. Think: The decimal needs to move left to change 7.09 to 0.00709, so the exponent will be negative. Think: The decimal needs to move 3 places. So 0.00709 written in scientific notation is 7.09 10–3. Check 7.09 10–3 = 7.09 0.001 = 0.00709 Try This Write 0.000811 in scientific notation. 0.000811 Move the decimal to get a number 8.11 between 1 and 10. 8.11 10 Set up scientific notation. Think: The decimal needs to move left to change 8.11 to 0.000811, so the exponent will be negative. Think: The decimal needs to move 4 places. So 0.000811 written in scientific notation is 8.11 10–4. Check 8.11 10–4 = 8.11 0.0001 = 0.000811 Example: Application A pencil is 18.7 cm long. If you were to lay 10,000 pencils end to end, how many millimeters long would they be? Write the answer in scientific notation. 1 centimeter = 10 millimeters, so 18.7 centimeters = 187 millimeters 187 mm 10,000 Find the total length. 1,870,000 mm Example Continued 1.87 10 Set up scientific notation. Think: The decimal needs to move right to change 1.87 to 1,870,000, so the exponent will be positive. Think: The decimal needs to move 6 places. The 10,000 pencils would be 1.87 10 6mm long, laid end to end. This is about one mile long. Try This An oil rig can hoist 2,400,000 pounds with its main derrick. It distributes the weight evenly between 8 wire cables. What is the weight that each wire cable can hold? Write the answer in scientific notation. Find the weight each cable is expected to hold by dividing the total weight by the number of cables. 2,400,000 pounds ÷ 8 cables = 300,000 pounds per cable Each cable can hold 300,000 pounds. Now write 300,000 pounds in scientific notation. Try This 3.0 10 Set up scientific notation. Think: The decimal needs to move right to change 3.0 to 300,000, so the exponent will be positive. Think: The decimal needs to move 5 places. 5 Each cable can hold 3.0 10 pounds. Lesson Quiz Write in standard notation. 1. 1.72 104 17,200 2. 6.9 10–3 0.0069 Write in scientific notation. 3. 0.0053 5.3 10–3 4. 57,000,000 5.7 107 5. A human body contains about 5.6 x 106 microliters of blood. Write this number in standard notation. 5,600,000

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posted: | 1/16/2013 |

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