MBT Sampler Flipbook

Using an AreaModel toMultiply Draw a picture of the product of a 2-digit and 2-digit number Level B 34 39 ©MathTeachersPress, Inc. Reproductionbyanymeans is strictlyprohibited 6. 42 3 32 ____ ________ 5. 21 3 32 ____ ______ 12 3 13 36 (3 3 12) 120 (10 3 12) 156 7. 23 3 32 1. 13 3 13 __ (3 3 3) ____ (3 3 10) ____ (10 3 3) __ ____ (10 3 10) Use eithermethod. 4. 31 3 12 __ __ (2 3 31) ______ (10 3 31) Usemethod 2 tofind theproducts. Usemethod 1 tofind theproducts. 12 13 12 12 (10+ 2) 3 13 (10+ 3) 6 (3 3 2) 30 (3 3 10) 20 (10 3 2) 100 (10 3 10) 156 Method1 3 3 2 Method 2 3 10 3 12 3 3 12 9. 22 3 43 3. 23 3 12 __ ____ __ __ __ ____ 8. 32 3 31 2. 12 3 24 __ (4 3 2) ____ (4 3 10) ____ (20 3 2) ____ __ (20 3 10) 10 10 3 2 3 3 10 10 3 10 Using Graph Paper to Multiply You canusebase tenblocks to solve the problem. Outline the rectanglemade by theblocks on graphpaper. Here are twopicturesof the problem ongraph paper. Objective: To draw a picture of the product of a 2-digit and 2-digit number. Materials: Base ten blocks, Place Value Mats (Masters 14 & 15), Centimeter Graph Paper (Master 4), dice Review multiplying 13 3 12 with base ten blocks from page 38. If you draw a picture of the multiplication problem 13 3 12 on centimeter graph paper, you can visualize the rule for multiplying 2-digit numbers. Outline a picture of 13 3 12 on your graph paper. Cover your outline with as few blocks as possible. (1 hundred, 5 tens and 6 ones) There are several smaller rectangles inside the larger rectangle. Outline each of the smaller rectangles. (a 10 3 10, 2 3 10, 3 3 10 and 2 3 3) Show two ways of recording the problem on the board: (1) with 4 multiplications 12 3 13 6 (3 3 2 = 6 ones) 30 (3 3 10= 3 tens) 20 (10 3 2 = 2 tens 100 (10 3 10 = 1 hundred) 156 (2) with 2 multiplications Point out how each part of the algorithm relates to the place value blocks. 12 3 13 36 (3 3 12) 120 (10 3 12) 156 Review the illustration together. Emphasize writing numbers in expanded notation (12 as 10 + 2 and 13 as 10 + 3) to develop further understanding of the multiplication algorithm. Shade in the different parts of the array to emphasize the partial products. Draw a picture for problem 1 to show the partial products. Have students continue to draw the arrays as needed. The method does not matter as long as they understand what they are doing. Have students work on the problems with a partner. Answer Key 1. 169 2. 288 3. 276 4. 372 5. 672 6. 1344 7. 736 8. 992 9. 946 - Multiplication Teamwork Divide the class into groups of 3 and assign a 1, 2, or 3 to each student. Each group rolls a 10-sided die four times to make a 2-digit by 2-digit problem. 2 3 1 3 4 Each player then works one of the three steps used in 2-digit multiplication 23 3 14 92 + 230 322 Player 1 multiplies by the digit in the ones place. Player 2 multiplies by the digit in the tens place. Player 3 adds the partial products. Each team scores a point for each step that is done correctly (3 points possible). The team with the most points after a set amount of problems wins. Journal Prompt Use graph paper to draw a rectangle to show the multiplication 20 3 14. Find the product from the graph. Skill Builders using Action Math Level B : 23-2, 23-3 Page 39 esson Uses: Base Ten Blocks Level B Sample Lesson Plan