Section 1.8. Operations with Fractions, Decimals and Percent

Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Multiply decimals Step 1. Determine the sign of the product. Step 2. Write in vertical format, lining up the numbers on the right. Multiply the numbers as if they were whole numbers, temporarily ignoring the decimal points. Step 3. Place the decimal point. The number of decimal places in the product is the sum of the number of decimal places in the factors. Step 4. Write the product with the appropriate sign. For Example: Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Multiplication by powers of 10 Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra #1 – 8: Multiply 1) 1.2 × 3.4 2) 4.2 × 5.7 3) −6.21 × 2.4 4) −3.14 × 2.3 5) 3.02556 × 103 6) 4.23587 × 104 7) 6.02 × 105 8) 5.1 × 103 Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Divide decimals Step 1. Determine the sign of the quotient. Step 2. Make the divisor a whole number by “moving” the decimal point all the way to the right. “Move” the decimal point in the dividend the same number of places—adding zeros as needed. Step 3. Divide. Place the decimal point in the quotient above the decimal point in the dividend. Step 4. Write the quotient with the appropriate sign. Remember these terms for division: For Example: #9-12: Divide 9) 7.68 ÷ 3.2 10) 17.22 ÷ 2.1 11) −21.73 ÷ 4.1 12) −13.33 ÷ 3.1 Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra A percent is a ratio whose denominator is 100. Percent means per hundred. We use the percent symbol, %, to show percent. Since a percent is a ratio, it can easily be expressed as a fraction. Convert percent to decimal Convert decimal to percent Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Convert decimal to a fraction Convert fraction to a decimal • Convert the fraction to a long division problem and perform the division. 1 For Example: Convert 4 to a decimal. Just set up the long division and perform the division. Answer: 1 4 = 0.25 Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Convert fraction to percent • • First perform long division to change the fraction to a decimal Second move the decimal two to the right to create a percent 1 For Example: Convert 4 to a percent. First: 1 Thus 4 = 0.25 Second move the decimal two places to the right to create a percent. 1 4 = 0.25 = 25% Convert fraction to percent – alternative method Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Convert percent to fraction • • • First convert the percent to a decimal by moving the decimal two places to the right Second create a fraction with the appropriate power of 10 in the denominator Third reduce the fraction For Example: Convert 0.345% to a fraction First: convert 0.345% to a decimal by moving the decimal two places to the right. 0.345% = 34.5 Second: right as a fraction. The denominator will be 10 as there is only one number after the decimal point. 345 10 0.345% = 34.5 = Third reduce the fraction: 0.345% = 34.5 = 345 10 Answer: 0.345% = = 5×69 5×2 = 69 2 69 2 Principal Square Roots Principal square root of 𝒎 ( √𝑚 ) is the positive number which when squared equals m. • If n is a positive number and n2 = m then √𝑚 = 𝑛 • NOTE √ the principal square root symbol requires a positive answer Principal Square Root Notation: √𝑚 is read “the principle square root of m. For example: √25 = 5 (since 5 is a positive number and 52 = 25) 13) Convert 30.251% to a decimal. 14) Convert 24.155 % to a decimal. 15) Convert 25.4% to a fraction. 16) Convert 12.3% to a fraction. 17) Write 0.12 as a fraction, reduced to lowest terms. 18) Write 0.24 as a fraction, reduced to lowest terms. 19) Write 6.123 as a percent. 4 21) Convert to a decimal. 5 23) Convert 6 to a percent. 24 20) Write 4.0225 as a percent. 2 22) Convert to a decimal. 5 24) Convert 9 12 to a percent. #25 – 26: Complete the table 25) 26) Fraction Decimal Percent Fraction Decimal Percent 3 ½ 4 0.8 0.28 75% 60% Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra Numbers can be classified into 5 broad categories. The categories are as follows: (Note that some numbers count in more than one category. Counting Numbers (Natural Numbers) Whole Numbers Integers Rational Number 1, 2, 3, 4, … 0, 1, 2, 3, 4… …, –3, –2, –1, 0, 1, 2, 3… 7 1 ̅̅̅̅̅̅, √16 Examples: 5, , , 0.97, 0.21 Irrational Number Examples: 𝜋, 𝑒, √8, 0.30312300003… 8 3 Counting numbers (also called natural numbers) are those used to count physical objects in the real world, such as 1, 2, 3, 4 ... • 6 is a counting number as it can be used to count many physical objects. Whole numbers are counting numbers with the number 0 added. • 9 is a whole number as it is a counting number • 0 is a whole number as 0 is included as a whole number Integers are all counting numbers, the opposite of every counting number and 0. • -3 is an integer as it is the opposite of the counting number 3 Rational numbers are numbers that can be written as a ratio of two integers. Its decimal form does stop or repeat. NOTE: Any number with a repeating decimal can be written as the ratio of two integers. Thus, any number with a repeating decimal is a rational number. 2 • is a rational number as it is a fraction with integers in the numerator and the denominator. 3 ̅̅̅̅ is a rational number as it is has a repeating decimal. With a bit of work, 42.534 ̅̅̅̅ can be • 42.534 written as the fraction • 42109 990 . -7 is a rational number as it can be written as −7 1 An irrational number is a number that cannot be written as the ratio of two integers. Its decimal form does not stop and does not repeat. • 15.435678234… is an irrational number, assuming the decimal does not terminate nor repeat. • Any number that contains 𝜋 (3.14 … )𝑜𝑟 𝑒 (2.718. . ) are irrational as the decimal does not terminate nor repeat. • √5 is an irrational number. Its decimal form does not stop, nor repeat. In fact, the square root of any number that is not a perfect square is an irrational number. Real number is any number that is either rational or irrational. • All numbers listed as examples above are real numbers. Section 1.8: Operations with Fractions, Decimals and Percent Chapter 1: Introduction to Algebra This diagram shows how the number groups relate to each other. For instance, every counting number is also a • • • • Whole number Integer Rational number Real number In fact, every number in one category is also a number in any category above it.