Lesson 4 Section 1.11, 1.13 Rounding Numbers Percent Whole Number Place Value 0, 0 0 0, 0 0 0, 0 0 0, 0 0 0, 0 0 0, 0 0 0, 0 0 0 sextillions hundred quintillions ten quintillions quintillions hundred quadrillions ten quadrillions quadrillions hundred trillions ten trillions trillions hundred billions ten billions billions hundred millions ten millions Millions hundred thousands ten thousands thousands hundreds tens ones The value of each digit to the right of the decimal point Ones Decimal Point Tenths Hundredths Thousandths Ten thousandths Hundred thousandths Millionths 7. 1 2 3 4 5 6 Rounding Numbers to a Particular Place Value To round a number to a particular place value: 1. If the digit in the next place to the right is less then 5, drop that digit and all other following digits. Use zeros to replace any whole-number places dropped. 2. If the digit in the next place to the right is 5 or greater, add 1 to the digit in the place to which you are rounding. Drop all other following digits. Use zeros to replace any whole-number places dropped.
Definition of a Percent Percent is a comparison of any number of parts to 100 part. The symbol for percent, % can be read out of each 100. How to Change a Percent to a Fraction To change a percent to a common fraction, divide the number before the percent symbol by 1 100. Note that this is equivalent to multiplying by 100. If a percent is greater than 100, the resulting fraction will be greater than 1. 3% = 3 100 25% = 25 100 = 1 4 80% = 80 100 = 4 5 120% = 120 100 = 1 20 100 = 1 1 5 33 1 3 % = 33 1 3 ( 1 100 ) = 100 3 1 100 = 1 3 66 2 3 % = 66 2 3 ( 1 100 ) = 200 3 1 100 = 2 3 How to Change a Percent to a Decimal To change a percent to a to a decimal, divide the number by 100 and remove the % symbol. This is equivalent to shifting the decimal point two places to the left. 5% = 0.05 150% = 1.50 25% = 0.25 0.07% = 0.0007 43% = 0.43 650% = 6.50
How to Change a Decimal to a Percent To change a decimal to a percent, multiply the number by 100 and add the % symbol. This is equivalent to shifting the decimal two places to the right. 0.5 = 50% 1.25 = 125% 2.8 = 280% 24 = 2400% 0.045 = 4.5% 0.005 = 0.5% How to Change a Fraction to a Percent To change a fraction to a percent, write the decimal equivalent of the fraction. Then use the changing a decimal to a percent rule to obtain the percent. 2 5 = 0.4 = 40% 1 = 0.5 = 50% 2 1 3 = 0.333 = 33 1 3 % 3 = 0.1875 = 18.75% 16 1 4 5 = 1.8 = 180% 2 3 = 0.666 = 66 2 3 %
Changing a Percent to a Decimal To change a percent to a decimal, move the decimal point two places to the left (divide by 100). Then remove the percent sign (%). Changing a Decimal to a Percent To change a decimal to a percent, move the decimal point two places to the right (multiply by 100). Write the percent sign (%) after the number. Changing a Fraction to a Percent 1. First, change the fraction to a decimal. 2. Then change this decimal to a percent. Changing a Percent to a Fraction 3. Change the percent to a decimal. 4. Then change this decimal to a fraction in lowest terms. Changing a Percent That Contains a Mixed Number to a Fraction 1. Change the mixed number to an improper fraction. 2. Then multiply this result by 1 and remove the percent sign (%). 100
Homework: HW: 4, 6, 14, 24 (p. 67), 2, 14, 20, 30, 48, 80 (p. 78-79) Review Exercises Round each number to a. The nearest hundred and b. The nearest ten. a. b. Round each number to a. The nearest hundred and b. The nearest ten. a. b. 63.76 63.76 100 63.76 60 2751 2751 2800 2751 2750 Round the number to the indicated place. 3,426.5823 Round to the nearest hundred: 3,426.5823 3,400 Round to the nearest ten: 3,426.5823 3,430 Round to the nearest unit: 3,426.5823 3,427 Round to the nearest tenth: 3,426.5823 3,426.6 Round to the nearest hundredth: 3,426.5823 3,426.58 Round to the nearest thousandth: 3,426.5823 3,426.582
Round the number to three significant digits. 367.52 367.52 368 Change the percent to a decimal. 29% Move the decimal point two places to the left and drop the percent symbol. 29% = 0.29 Change the percent to a decimal. 0.29% Move the decimal point two places to the left and drop the percent symbol. Change the percent to a decimal. 0.29% = 0.0029 25 2 3 % Move the decimal point two places to the left and drop the percent symbol. 25 2 3 % = 77 3 % = 25.66666 % = 0.2566666 = 0.256 Change the decimal to a percent: 0.465 Move the decimal point two places to the right and attach the percent symbol. 0.465 = 46.5%
Change the fraction to a percent: 4 7 Use long division and divide 4 by 7. When the division is carried out to the hundredths place and the remainder is not zero, write the remainder in fraction form, with the remainder over the divisor. 0.57 7)40 35 50 49 1 4 7 = 0.57 1 7 = 57 1 7 % Change the percent to a fraction or a mixed number in lowest terms: 10 3 4 % 10 3 4 % = 43 4 % = 43 4 1 100 = 43 400