Difference between revisions of "Convert to Percentage"
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== Steps == | == Steps == | ||
===Estimating Percentages Without a Calculator=== | ===Estimating Percentages Without a Calculator=== | ||
| − | #Use simple addition and subtraction to estimate a percentage quickly. This is most helpful when figuring out tips, or any other time you might not have a calculator available. Percentages can be added and subtracted as long as they are percentages of the same thing (ie, 5% of a 15lb turkey is cannot be added to 20% of a 5lb turkey). This trick makes it easy to guess simple percentages.<ref>http://www.mathcentre.ac.uk/resources/uploaded/mc-ty-percent-2009-1.pdf</ref> | + | #Use simple addition and subtraction to estimate a percentage quickly. This is most helpful when figuring out tips, or any other time you might not have a calculator available. Percentages can be added and subtracted as long as they are percentages of the same thing (ie, 5% of a 15lb turkey is cannot be added to 20% of a 5lb turkey). This trick makes it easy to guess simple percentages.<ref name="rf1">http://www.mathcentre.ac.uk/resources/uploaded/mc-ty-percent-2009-1.pdf</ref> |
#*For example, say you want to leave a 20% tip with your lunch bill, which is $23.50. With a few simple tricks, you can get an estimate of a 20% tip with relative ease. | #*For example, say you want to leave a 20% tip with your lunch bill, which is $23.50. With a few simple tricks, you can get an estimate of a 20% tip with relative ease. | ||
#Move the decimal one place to the left to find 10% instantly. This is the easiest way to get rough percentages without a calculator. To do it, simply slide the decimal over one place to the left. So 10% of $23.50 is '''$2.35.''' Remember, there is always a decimal place at the end of a number, so 25 could also be thought of as 25.00. | #Move the decimal one place to the left to find 10% instantly. This is the easiest way to get rough percentages without a calculator. To do it, simply slide the decimal over one place to the left. So 10% of $23.50 is '''$2.35.''' Remember, there is always a decimal place at the end of a number, so 25 could also be thought of as 25.00. | ||
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#*25% of a number is always the number divided by 4. | #*25% of a number is always the number divided by 4. | ||
#*50% of a number is always the number cut in half. | #*50% of a number is always the number cut in half. | ||
| − | #*33% of a number is always the number divided by 3.<ref>http://study.com/academy/lesson/what-is-a-percent.html</ref> | + | #*33% of a number is always the number divided by 3.<ref name="rf2">http://study.com/academy/lesson/what-is-a-percent.html</ref> |
===Converting Fractions into Percentages=== | ===Converting Fractions into Percentages=== | ||
#Know that percentages are just fractions out of 100. All a percentage is a simple way to display a fraction whose bottom number (known as the denominator) is 100. A percentage tells you how many things you would have if you had 100 total. For example, say 25% of your apple harvest is always spoiled. That means for every 100 apples you harvest, 25 of them will be spoiled, or 25/100. Converting fractions allows you to find percentages in the real world, such as what percentage of apples is spoiled if you get 450 bad apples out of 2,500. | #Know that percentages are just fractions out of 100. All a percentage is a simple way to display a fraction whose bottom number (known as the denominator) is 100. A percentage tells you how many things you would have if you had 100 total. For example, say 25% of your apple harvest is always spoiled. That means for every 100 apples you harvest, 25 of them will be spoiled, or 25/100. Converting fractions allows you to find percentages in the real world, such as what percentage of apples is spoiled if you get 450 bad apples out of 2,500. | ||
| − | #*If your fraction already has a denominator of 100, like 25/100, the top number is the percentage.<ref>http://www.studyzone.org/mtestprep/math8/e/estpercent6l.cfm</ref> | + | #*If your fraction already has a denominator of 100, like 25/100, the top number is the percentage.<ref name="rf3">http://www.studyzone.org/mtestprep/math8/e/estpercent6l.cfm</ref> |
| − | #*1% means that there is "1 per every 100."<ref>https://www.mathsisfun.com/percentage.html</ref> | + | #*1% means that there is "1 per every 100."<ref name="rf4">https://www.mathsisfun.com/percentage.html</ref> |
#Create a fraction from word problems. Sometimes you are not given the fraction, and you need to make it yourself. The hardest part here is figuring out which number goes on top, and which on bottom. The bottom number is always your "whole amount." It is your total apple harvest, the amount on the restaurant bill, the number of slices of pie, etc. This is the number you're getting a percentage of. The following examples show how to set up fractions: | #Create a fraction from word problems. Sometimes you are not given the fraction, and you need to make it yourself. The hardest part here is figuring out which number goes on top, and which on bottom. The bottom number is always your "whole amount." It is your total apple harvest, the amount on the restaurant bill, the number of slices of pie, etc. This is the number you're getting a percentage of. The following examples show how to set up fractions: | ||
#*Jaime has 4,000 songs. If 500 of them are by the Grateful Dead, what percentage of his music is by the San Francisco jam legends? | #*Jaime has 4,000 songs. If 500 of them are by the Grateful Dead, what percentage of his music is by the San Francisco jam legends? | ||
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#*Multiply this number by 100 to get the percentage. | #*Multiply this number by 100 to get the percentage. | ||
#**1.75 x 100 = 175 | #**1.75 x 100 = 175 | ||
| − | #*'''You ate 175% of the recommended daily calories.'''<ref>http://www.purplemath.com/modules/percntof.htm</ref> | + | #*'''You ate 175% of the recommended daily calories.'''<ref name="rf5">http://www.purplemath.com/modules/percntof.htm</ref> |
===Converting Percentages to Back to Amounts=== | ===Converting Percentages to Back to Amounts=== | ||
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#**20% → .20 | #**20% → .20 | ||
#**10 divided by .20 = 50. | #**10 divided by .20 = 50. | ||
| − | #**'''The class has 50 marbles total.'''<ref | + | #**'''The class has 50 marbles total.'''<ref name="rf1" /> |
#Use examples to practice. You find a blouse that you love for $50, but it is on sale today, 15% off. How much will the blouse cost, total? | #Use examples to practice. You find a blouse that you love for $50, but it is on sale today, 15% off. How much will the blouse cost, total? | ||
#*Convert 15% into a decimal. | #*Convert 15% into a decimal. | ||
