Grade2Unit4 2015-2016

Grade2Unit4

ApplyingBaseTenUnderstandingVolume1Issue4

ReferencesHelpfulLinks:MathMagician(FactPractice)http://oswego.org/ocsd-web/games/mathmagician/maths1.htmlABCYa(CountingMoney)http://www.abcya.com/counting_money.htmLearningBox(PlaceValue)http://www.learningbox.com/Base10/BaseTen.htmlJohnnie’sMathPage(Facts&OperationsPractice)http://jmathpage.com/topics/jmp2ndgradeoperations.htmlJohnnie’sMathPage(DevelopingNumberSense)http://jmathpage.com/topics/jmp2ndgradenumbersense.htmlMathGrade2TextbookConnection:Ch.6,Lessons6.1-6.3,6.8Ch.7,Lessons7.1-7.3Ch.8,Lessons8.1-8.3TextbookOnline:http://connected.mcgraw-hill.com/connected/login.doStudentUserID:ccsd(studentID)Password:cobbmath1

DearParents,Duringthisunityourchildwillbeexploringadditionandsubtractionoftwoandthree-digitnumbersandwillgettotrymanydifferentstrategiesbasedonplacevalueandunderstanding.Pleasekeepinmindthatwhilethesestrategiesmaybedifferentfromthewayyouarefamiliarwithaddingandsubtracting,thepurposeofthesestrategiesistobuildastrongfoundationofplacevaluewhencomputingsostudentswillunderstandwhythetraditionalmethodsofadditionandsubtractionworkbutwillhaveavarietyofstrategiesthancanuseforflexibilityandefficiency.Studentswillalsobeworkingwithmoneyandtheyusetheirplacevalueunderstandingtosolvesimplewordproblemsinvolvingmoney.

ConceptsStudentswillUseandUnderstand• Continuetorepresentandsolveproblemsinvolvingadditionandsubtraction.• Addupto4two-digitnumbers.• Understandandapplypropertiesofoperationsandtherelationshipbetweenadditionandsubtraction(inverseoperations).• Becomefluentwithmentallyaddingorsubtracting10or100toagiventhree-digitnumber.• Knowthemultiplemeaningsforaddition(combine,join,andcounton)andsubtraction(takeaway,remove,countback,andcompare)• Recognizeanduseplacevaluetomanipulatenumbers.• Countwithpennies,nickels,dimes,anddollarbills.• Solveproblemsusingmentalmathstrategies.

Vocabulary• expandedform:Amulti-digitnumberisexpressedinexpandedformwhenitiswrittenasasumof

single-digitmultiplesofpowersoften.Forexample,643=600+40+3.basetenblocks:Amanipulativeusedtobuildnumbersandtohelpwithadditionandsubtractionattheconceptuallevel.placevalue:Thevalueofadigitbasedonitsplaceinanumber.symbols:+,-,=,join:toputtogether(add)separate:totakeapart(subtract)total:Thenumberwhensetsarecombined.sum:Thetotalwhennumbersareadded.inverseoperations:theinverseoperationsforadditionissubtraction;theinverseoperationforsubtractionisaddition.differenceTheresultwhenonenumberissubtractedfromanother.equationAmathematicalexpressionwhereonepartisequaltotheotherpart.Example:50+26=70+6.

• Fluentlyisaccuratelyandefficiently.

Grade2Unit4 2015-2016

Symbols+addition

-subtraction

=equal

Example1Studentsaregoingtousetheirunderstandingofplacevalueandexpandedformfromunit1tohelpthemaddandsubtractwithin100fluentlyandwithin1000usingstrategiesbasedonplacevalue.Thefollowingisacommonwaystudentsmightadd2or3-digtnumbers.

2ndgradestudentsneedtounderstandthattheycangrouphundreds,tensandonesandtheorderdoesnotmatter.DrawingBaseTenblockstohelpthemsolvethisproblemisalsocommon.Keepinmindthat“naked”numbersareabstractandgivenacontextcanhelpstudentsconceptualizethenumbersmoreeasily.Insteadofusingnumberssuchas248and345,say248pencilsand345pencils.

Example2Anopennumberlineallowsstudentstoaddorsubtractinchunksandservesasavisualrecordingmethodtokeeptrackofthecomputation.Studentsareencouragedtousethisstrategyinawaythatmakessensetothem–numbersmaybebrokenapartinmanydifferentways.Thisisoneexampleofusinganopennumberlinetomodeladdition.Studentsbecomemoreefficientintheirmodelsastheirknowledgesolidifies.

Example3Studentscanalsouseanopennumberlinetomodeladdinguptofindthedifferencebetween236and79.

Example4Studentsstarttoworkwithtwo-stepwordproblemsusingsimplenumbers.Promotestudentsreading,thinkingaboutandvisualizing1sentenceatatime:Josehad24ticketsafterplayingskiball.Heused7ofticketstobuyarubberballandsomemoretobuyaneraser.Josehas9ticketsleft.Howmanyticketsdidtheerasercost?

Grade2Unit4 2015-2016

ActivitiesatHome

• Letyourchildcountthechangefromyourpocketsorpurse.• Encourageyourchildtopracticeskipcountingby5’s,10’s,and100’sstartingatnumbersotherthan0.For

example,skipcountby5’sfrom35to50orskipcountby10’sfrom78to128.• Havestudentsmentallyadduptofour2-digitnumbers.Forexample,add20+30+10.Progresstoaddingmore

difficult2-digitnumberssuchas27+15+10+12.Students• Checkoutthewebsitesfrompage1.