New SAT Math Workbook

05 100 34 34 34 means 34 out of 100 or which is

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Unformatted text preview: is equivalent to or .034 100 1000 c 1 ⋅ c or .01c c% means c out of 100 or , which is equivalent to 100 1 100 1 1 1 ⋅ .25 or .0025 % means out of 100 or 4 , which is equivalent to 4 4 100 100 5% means 5 out of 100 or To change a percent to a decimal, therefore, we must move the decimal point two places to the left, as we are dividing by 100. Example: 62% = .62 .4% = .004 3.2% = .032 To change a decimal to a percent, we must reverse the above steps. We multiply by 100, which has the effect of moving the decimal point two places to the right, and insert the percent sign. Example: .27 = 27% .012 = 1.2% .003 = .3% To change a percent to a fraction, we remove the percent sign and divide by 100. This has the effect of putting the percent over 100 and then simplifying the resulting fraction. Example: 25% = 25 1 = 100 4 70 7 70% = = 100 10 5 1 .5 .5% = = = 100 1000 200 To change a fraction to a percent, we must reverse the above steps. We multiply by 100 and insert the percent sign. Example: 44 = ⋅ 100 % = 80% / 55 25 33 75 1 = ⋅ 100 % = % = 37 % / 88 2 2 2 20 www.petersons.com 72 Chapter 5 Some fractions do not convert easily, as the denominator does not divide into 100. Such fractions must be changed to decimals first by dividing the numerator by the denominator. Then convert the decimal to a percent as explained on the previous page. Divide to two places only, unless it clearly comes out even in one or two additional places. Example: .47 8 1 = 17 8.00 = 47 % 17 17 68 1 20 1 19 ) .032 4 = 125 4.000 = 3.2% 125 3 75 250 250 ) 1 Certain fractional and decimal equivalents of common percents occur frequently enough so that they should be memorized. Learning the values in the following table will make your work with percent problems much easier. PERCENT 50% 25% 75% 10% 30% 70% 90% 1 3 2 66 % 3 2 16 % 3 1 83 % 3 DECIMAL .5 .25 .75 .1 .3 .7 .9 .33 .66 .16 FRACTION 1 2 1 4 3 4 1 10 3 10 7 10 9 10 1 3 2 3 1 6 5 6 1 5 2 5 3 5 4 5 1 8 3 8 5 8 7 8 33 % .83 20% 40% 60% 80% 1 2 1 37 % 2 1 62 % 2 1 87 % 2 .2 ....
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This note was uploaded on 08/15/2010 for the course MATH a4d4 taught by Professor Colon during the Spring '10 term at Embry-Riddle FL/AZ.

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