EXT 3-6 Sampler

52 Grade5 PartB Lesson25, 5ETeacherGuide 71 71 ©Math TeachersPress, Inc.,Reproduction by anymeans is strictly prohibited. Multiplying Fractions by Fractions paper folding of = cutting the shadedpart of a fractionbar intoequal parts Rule: Multiply the numerator by thenumerator and the denominator by thedenominator. Simplify the answer. } } Here are someways tomultiply a fraction by a fraction. Use the pictures to find the products. 12. Derrickmade a pan of brownies and cut them into 2 equal parts. He then cut each part into 10 equal pieces and ate one of the pieces. What fraction of the brownies did he eat? ____________ 13. Rosa had of an apple pie. She ate of the pie after school. What fraction of thewhole pie did she eat after school? ____________ of = 1. 2. 3. of = of = of = Draw in dotted lines to show themultiplication. Shade to show the solution. 4. 5. of = ______ of =______ 6. of = _________ 9. of = _________ 7. of = _________ 10. of = _________ 8. of =_________ 11. of =_________ Multiply. Part B 1 10 1 6 1 20 1 12 1 12 1 20 2 15 1 9 3 5 1 30 12 20 = 9 20 4 15 1 5 1 3 1 15 of the brownies of the pie Objective19: To find thepattern formultiplying fractions. To relate theword “of” to theoperationofmultiplication. Materials: Paper, FractionBars orFractionStrips (Master 16) Pattern forMultiplyingFractions Students can learn the algorithmor rule formultiplying fractionswith little conceptual understandingbecause the ideas they learned forwholenumbermultiplication also workwith fractions (multiply thenumerators;multiply the denominators). Therefore, instruction shouldbeginwith various problem-solving strategies that help students find themultiplicationpattern. These strategies alsohelp studentsunderstandwhy a fractionof a fractionor a fractionof awholenumberwill be less than theoriginal number. Writeon theboard: Youhaveone-half of apizza left over fromdinner. For abedtime snack, you eat one-half of your leftoverpizza. What fractional part of thewholepizzadidyou eat for abedtime snack? Ask students to read theproblem anddiscusswith a partnerdifferentways to solve theproblem. Somepossible solutions are actingout theproblemwith a real pizza, modeling theproblemwith apieceof clayor round tortilla, drawing apicture, andpaper folding. Draw apicture: Paper folding: Fold a square into2 equal parts (each side represents oneunit). Eachpart is½. Fold the½of the square into two equal parts. Each small part is¼. Writeon theboard: 1 2 of 1 2 1 4 Whydoes itmake sense to say that of means multiplication? (Becausemultiplying thedenominators gives you the total number of parts andmultiplying the numerators gives you thenumber of parts taken.) Demonstrate the sameproblemusing½FractionBars and draw the solutionon theboard: 1 4 1 2 1 4 1 2 What is thepattern formultiplying fractions? (Multiply thenumerators andmultiply thedenominators. Simplify if possible.) Read the information at the topof thepage together. Fold a squarepieceof paper todemonstrate¼of½ ⅛. Draw apictureof a fractionbardivided intoonehalves and shadeonehalf. Ifwedrawdotted lines to show¼of½, what fractional part is ¼ of½? (⅛)Have studentsdraw dotted lines to solveproblem4.Note that the answers to someproblemswill need tobe simplified. Journal Prompt When two fractions aremultiplied,what can you say about the sizeof the resulting fraction? Give an example to justifywhat happens.Usediagrams, words, and/or symbols. Skill Builders 19-2 1 2 1 2 1 4 1 2 of or - MultiplyingFractionsbyFractions Excellent preparation for Smarter Balancedand PARCCAssessments. Drawing pictureshelps studentsunder- standwhy multiplyinga fraction times a fraction results inan answer that is less than the fraction.