Proportion and percentage

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1、ProportionandPercentageRatioandProportionLetxbethenumberofpotatoesrequiredtoserve28people.Crossmultiply4x=5(28)4x=140Example1Arecipethatserves4peopleuses5potatoes.Howmanypotatoesareneededtoserve28people?Sincetherecipeisthesame,wehavetwoequivalentratios:#ofpeople:#ofpotatoes:#1#2#3#4Divideby4to

2、findxx=35potatoesdirectproportion:Anincreaseordecreaseinonequantitywillleadtoanincreaseordecreaseoftheotherquantityinthesameproportion.Ittakes6people8daystodoapieceofwork.Howlongwillittake12peopletodothesamepieceofwork,assumingtheyallworkequallyhard?Example2THEANSWER:4daysInverseproportion:One

3、quantityincreasesinthesameproportionastheotherquantitydecrease.PercentageThisphrasepercentcomesfromtheLatin‘percenturi’whichmeans‘asperhundred’.Apercentageisaratioinwhichthesecondquantityisalways100Apercentageisafractioninwhichthedenominatorisalways10016or16.00%1.a.Find20%of80.2.a.Whatis35%of2

4、0?7or7.003.a.Thereisadiscountof25%offona$60pairofshoes.Howmucharetheshoes?$454.a.Ashirtcost$30plus7%tax.Whatisthetotalcost?$32.10WritingapercentageasafractionExamples:1.5%2.250%ProfitandlossLoss=costprice–sellingpriceProfit=sellingprice–costpriceExamples:1.Ashopkeeperbuysanarticlefor＄500andsel

5、lsitfor＄600，whatisthepercentageprofit?Profit=sellingprice–costprice=＄600-＄500=＄1002.Apersonbuysacarfor＄16000andsellsitfor＄12000.calculatethepercentageloss.Loss=costprice–sellingprice=＄16000-＄12000=＄4000