AddingandsubtractingfractionsAddingandsubtractingfractionsiseasierthanyoumightthink.Youjustneedtorememberthissimplemethod:Step1:
Makesurethedenominators(numbersonthebottom)arethesameonbothfractions.Dothisbyfindingthelowestcommonmultipleofbothdenominators.Forexamplewith:!!
+ !!Thelowestcommonmultipleof3and2is6.
Step2:
Thenmultiplybothdenominatorsuptothatnumber(ifindoubtjustmultiplythedenominatorsbyeachother).Makesureyouthenrememberthegoldenruleoffractions–whateveryoudotothedenominator,youmustalsodotothenumerator(thenumberoftop).Soyouneedtomultiplythenumeratorsbythesamenumberasthedenominator.
Intheexampleof!!
+ !!youhavemultipliedthe3by2togetto6andthe2
by3togetto6,soyouneedtodothesametothenumerators:
! × !! ×!
+ ! × !! × !
=Thisgives:26 +
36
Step3:
Thefinalstepisthensimplytoaddorsubtractacrossthenumerators.Sothefinalsumis:2+ 36 =
56
Rememberthatthemethodisexactlythesameforsubtractingfractions.Allyouneedtododifferentlyissubtractthenumeratorsatstep3.Usewhatyouhavelearntheretohaveagoatthepracticequestionsonthenextpage.
Addingandsubtractingfractions–practicequestions
1. !!+ !
!=
2. !!+ !
!=
3. !!+ !
!=
4. !!+ !
!=
5. !!+ !
!=
6. !!− !
!=
7. !!− !
!=
8. !!− !
!=