Scientific Notation: Understanding Large and Small Numbers, Lecture notes of Mathematics

Download Scientific Notation: Understanding Large and Small Numbers and more Lecture notes Mathematics in PDF only on Docsity! Scientific Notation In the sciences, many of the things measured or calculated involve numbers that are either very large or very small. As a result, it is inconvenient to write out such long numbers or to perform calculations long hand. In addition, most calculators do not have enough window space to be able to show these long numbers. To remedy this, we have available a short hand method of representing numbers called scientific notation. The chart below gives you some examples of powers of 10 and their names and equivalences. Exponent Expanded Prefix Symbol Name Fraction 10-12 0.000000000001 pico- p one trillionth 1/1,000,000,000,000 10-9 0.000000001 nano- n one billionth 1/1,000,000,000 10-6 0.000001 micro- u one millionth 1/1,000,000 10-3 0.001 milli- m one thousandth 1/1,000 10-2 0.01 centi- c one hundredth 1/100 10-1 0.1 deci- d one tenth 1/10 100 1 ------ ------ one -------- 101 10 Deca- D ten -------- 102 100 Hecto- H hundred -------- 103 1,000 Kilo- k thousand -------- 104 10,000 ------ 10k ten thousand -------- 105 100,000 ------ 100k one hundred thousand -------- 106 1,000,000 Mega- M one million -------- 109 1,000,000,000 Giga- G one billion -------- 1012 1,000,000,000,000 Tera- T one trillion -------- 1015 1,000,000,000,000,000 Peta- P one quadrillion -------- Powers of 10 and Place Value.......... Multiplying by 10, 100, or 1000 in the following problems just means to add the number of zeroes to the number being multiplied. This is because our number system is based on 10. The chart above shows the powers of 10 you are most likely to encounter in your science studies. 1. 35 x 10 → 35 + 0 → 350 2. 6 x 100 → 6 + 0 + 0 → 600 3. 925 x 10 → 925 + 0 → 9,250 4. 42 x 1000 → 42 + 0 + 0 + 0 → 42,000 5. 691 x 1000 → 691 + 0 + 0 + 0 → 691,000 Places to right of the decimal point are called decimal fractions. The negative exponents shown under the negative exponents shown under the Exponents column above tell you to divide by that number. Examples: 10-1 = 1/10 = .1 10-2 = 1/102 = 1/100 = .01 10-3 = 1/103 = 1/1000 = .001 You know that the value of each digit depends on which place it occupies. For example, the 5 in 5628 has the value of 5 thousand, while the value of the 1 in 1586000 is 1 million. A number can be expanded according to the place value it holds: Example A: 589 = 5(100) + 8(10) + 9(1) 67.32 = 6(10) + 7(1) + 3(.1) + 2(.01) For larger numbers, it is easier to use exponents for the place values. Example B: 96,734,000 = 9(107) + 6(106) + 7(105) + 3(104) + 4(103) Multiplying and Dividing a Number By a Power of 10 In the last section you saw how trailing zeroes are carried along when you multiply by powers of 10. Adding trailing zeroes on is just like moving the decimal point. To multiply a number by a power of 10, move the decimal point to the right the same number of places as the exponent. 49 x 100 = 4,900 49.00 x 100 = 4,900. Since you are multiplying by 100 (102), move the decimal point 2 places to the right. Add zeroes when necessary . 325 x 1,000 = 325,000 325.000 x 1000 = 325,000 You can multiply by 1000 (103) by moving the decimal point 3 places to the right. Add zeroes when necessary. Dividing by powers of 10 can be viewed in the same manner. To divide a number by a power of 10, move the decimal point to the left the same number of places as the exponent. 6,000 = 60.00 = 60 100 100 can be written as 102 , so you would move the decimal point 2 places to the left. 40,000 = 4.0000 = 4 10,000 10,000 is the same as 104, so you would move the decimal point 4 places to the left. To make sense about which way to move the decimal point use the following tips: 1. By moving the decimal point to the right, you are making the number larger. 2. By moving the decimal point to the left, you are making the number smaller. Example Set 4. Complete the table using the technique of moving the decimal point to multiply and divide. Number to Use x 10 ÷ 1,000 x 1,000 Ex. 308.5 3,085 0.3085 308,500 Ex. 5.004 50.04 0.005004 5,004 a) 730.2 b) 2.105 c) 45 d) 0.08 Scientific Notation The population of California in 1990 was estimated at 29,600,000. Another way of writing large numbers like this, as well as small numbers, is to use a shorthand method called scientific notation. Thus, the population of California can be written as 2.96 x 107. Scientific notation consists of two parts: a number with a value between 1 and 10 multiplied by a power of 10. A.) 5,000,000,000 in scientific notation is 5 x 109. This is breaking the number into the digit times its place value. (Count the O's.) B.) 0.004 in scientific notation would be 4 x 10-3 The 4 is in the thousandths place, so multiplying by 10-3 (1/1000) is the same as dividing by 103 (1,000). C.) 8,200 in scientific notation is 8.2 x 103. Move the decimal point so that there is only one non-zero digit to the left of it. How many places did you move it? In what direction? 3 to the left (divided). Compensate for the division by multiplying the same number, 8.2 x 103. D.) 0.00029 in scientific notation is 2.9 x 10-4. Move the decimal point so that there is only one non-zero digit to the left. How many places did you move it? In what direction? 4 to the right (multiplied) Compensate for the multiplication by dividing the same number 2.9 x 10-4. E. 4.39 x 107 written the long way would be 43,900,000. The single digit 4 is before the decimal point. Add enough zeros so that the 4 is in the 107 place. 43,900,000 (The 107 place means there are 7 digits between the 4 and the decimal point.) Example Set 5. Write the following numbers in scientific notation. a) 70,000 _____________________________ b) 300,000 _____________________________ c) 800,000,000 _____________________________ d) 9 ,000,000,000 _____________________________ e) 0.008 _____________________________ f) 0.00003 _____________________________ g) 0.000009 _____________________________ h) 0.0000002 _____________________________