EXT 3-6 Sampler

46 Grade5 Finding theLeastCommonMultiple Objective12: Tousemultiple strips to find the least commonmultiple. Materials: TableofMultiples (Master 14) Vocabulary: least commonmultiple (LCM), lowest commondenominator (LCD),multiple Discover thePattern Distribute theTableofMultiples (Master 14) to students: Lookat yourTableofMultiples.Theproduct of a numberandanywholenumber is calledamultiple . Each rowgives themultiplesof the firstnumber in the far left column.What are the first fivemultiplesof 2? (2, 4, 6, 8, 10) What are themultiplesof 3? (3, 6, 9…) Are thereanynumberswhicharemultiplesof 2and3? (6, 12, 18, 24). We say theseare commonmultiplesof 2 and3.Which is the least of these commonmultiples? (6) We say that 6 is the least commonmultiple for2and3. Continue this series of questions to find the least commonmultiple for 3 and4, 4 and6, 6 and8, 9 and10. Whenyouareaddingor subtracting fractions, they must alwaysbedivided into the samenumberofparts. Wehavealreadynoticed that fractionbarsof the same colorhavebeendivided into the samenumberofparts. Whenwriting fractions, this leastnumberofparts is called the lowest commondenominator (LCD) . The lowest commondenominatorand least commonmultiple are the same.What is the lowest commondenominator for two fractionshaving thedenominatorof 2and3? (6) 3and4? (12) Have studentswork inpairs.Haveboth students pick any twonumbers except thenumber “1”. Thenhave them underline the commonmultiples and circle the least commonmultiple. Read the information at the topof thepage together. Have studentsuse theTableofMultiples (Master 14) to complete thepage.Doproblem5 together tomake sure studentsunderstand that they find theLCD first and then change thenumerators to create equivalent fractions.Note that problems 7, 8, 9, 13, and15 all havedenominators greater than12, but oneof thenumbers is the lowest commondenominator. Skill Builders 12-2 X 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 2 4 6 8 10 12 14 16 18 20 22 24 3 6 9 12 15 18 21 24 27 30 33 36 4 8 12 16 20 24 28 32 36 40 44 48 5 10 15 20 25 30 35 40 45 50 55 60 6 12 18 24 30 36 42 48 54 60 66 72 7 14 21 28 35 42 49 56 63 70 77 84 8 16 24 32 40 48 56 64 72 80 88 96 9 18 27 36 45 54 63 72 81 90 99 108 10 20 30 40 50 60 70 80 90 100 110120 11 22 33 44 55 66 77 88 99 110 121132 12 24 36 48 60 72 84 96 108 120 132144 1 2 3 4 5 6 7 8 9 10 11 12 - Lesson12, 5ETeacherGuide 37 37 ©Math TeachersPress, Inc.,Reproduction by anymeans is strictly prohibited. Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24 Multiples of 4: 4, 8, 12, 16, 20, 24, 28 Least commonmultiple: 12 is the same as . is the sameas . You cannotaddorsubtract fractionsunless theyaredivided into the samenumberofparts.What is the least numberofparts that 3 1 sand 4 1 s can both bedivided into? Finding theLeast CommonMultiple Jameswatched thenews onTV for of an hour before school. Hewatchedabaseball game after dinner for of an hour. Didhe spendmore timewatching thenews or the baseball game? More time spent watching ______________ _____ > _____ Rewrite eachpair of fractions tohavea lowest commondenominator (LCD). Find the least commonmultiple (LCM) for eachpair of fractions. 1. and LCM= _____ 4. and LCM=_____ 2. and LCM= _____ 3. and LCM=_____ 5. = ___ = ___ 6. = ___ = ___ 7. = ___ = ___ 8. = ___ = ___ 9. = ___ = ___ 10. = ___ = ___ 11. = ___ = ___ 12. = ___ = ___ 13. = ___ = ___ 14. = ___ = ___ 15. = ___ = ___ 16. = ___ = ___ LeastCommon Multiple (LCM) or LowestCommon Denominator (LCD) x__ x__ x__ x__ = = 17. Another name for least commonmultiple is_______________________________ . 1 3 1 4 16 24 6 16 12 16 9 12 3 6 15 18 6 14 4 4 3 3 9 12 10 14 15 18 15 20 4 6 9 24 5 16 5 16 10 12 4 6 4 18 5 14 5 12 3 14 3 18 20 20 5 6 baseball 4 lowest commondenominator 12 10 12 Students find the least common multipleof 2 numbers and maybe called the lowest common denominator.