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Module 3 Lesson 3 Use Familiar Facts to multiply & divide; Use a letter (variable) to represent unknown numbers. Familiar Facts! 15 5 x 3 = _______ Now write a division sentence! 15 ÷ 3 = 5 12 4 x 3 = _______ 12 ÷ 3 = 4 Now write a division sentence! Familiar Facts! 14 7 x 2 = _______ Now write a division sentence! 14 ÷ 2 = 7 18 6 x 3 = _______ 18 ÷ 3 = 6 Now write a division sentence! What is the missing factor? 5 x 2 =10 ____ 2 x 10 20 = ____ 2 x3=6 ____ 6 x3 18 = ____ 8 x 2 = 16 ____ 9 x5 45 = ____ Multiply: Use the Distributive Property 9 18 27 36 45 5 10 15 20 25 30 35 40 45 What thegroups two multiplication sentences How are many of 9 are there? 9 x 5by = 9s 45 and 5 x 9 = 45 Now count forCount this array? by 5s to find out. Multiply: Use the Distributive Property How many 9 xgroups 6 =45 45 54++of and 96! 6= 9= 54 are 6 ??? x9 there = 54now? . Make 10s 6 = 10 4 + ___ 1 = 10 9 + ___ 2 = 10 8 + ___ 3 7 + ____ = 10 2+ 8 ___ = 10 5 5 + ___ = 10 7 3 + ____ = 10 4 = 10 6 + ___ Problem of the Day 24 people line up to use canoes at the park. Three people can ride in each canoe. How many canoes will they need? 3 3 6 3 9 12 3 15 3 18 3 21 3 24 3 24 24 people people == ?8 canoes canoes Use a VARIABLE A VARIABLE is a letter we use to represent an unknown number in a math problem. Now Writewrite the problem the problem of the using dayaas letter multiplication to represent sentence the unknown with an number: unknown number: 3 x3_____ x c = 24 = 24 Use a VARIABLE Now let’s re-solve the Problem of the day, using the variable (c) instead of a question mark (?) … Use a variable 24 people line up to use canoes at the park. Three people can ride in each canoe. How many canoes will they need? 3 6 9 12 15 18 21 24 3 c==2424 3 xxcneed 24 people 8 canoes c=8 Use more VARIABLES 21 third are grouped intomath threes to Let’s try graders using variables in other visit the planetarium. How many groups of operations … third graders are there? Talk to your table partner about which letter you would use to represent the unknown number. Now write and solve an equation using your variable. Use more VARIABLES 21 third graders are grouped into threes to visit the planetarium. How many groups of third graders are there? 21 ÷ 3 = g g=7 Use more VARIABLES Notice how we wrote the solution to the problem: g = 7. This is the format we use when writing the answer to a math problem with a variable. 21 ÷ 3 = g g=7 Problem Set What does YOUR variable equal?
