Double Digit Math
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This document provides examples and steps for performing addition, subtraction, and multiplication through mental math and process math. It includes modeling addition and subtraction with carrying and regrouping, as well as examples for students to practice. The key strategies emphasized are adding and subtracting by tens and ones, counting differences by tens then ones, and trying mental math before using algorithms.
Double Digit Math
- 1. Process Math and Mental MathProcess Math and Mental Math
- 2. Model: 50 + 30 = Steps: 1.think 30 2.add 5 tens…(5 fingers) say 40, 50, 60, 70, 80 3.the answer is 80 Practice: 60 + 10 = _____ 30 + 20 = _____ 20 + 40 = _____ 50 + 40 = _____ 80 70 50 60 90
- 3. Model: 53 + 35 = Steps: 1.think 35 2.add 3 ones…(hold up 3 fingers) 36, 37, 38 3.add the 5 tens…(hold up 5 fingers) 48, 58, 68, 78, 88 4.the answer is 88 Practice: 62 + 11 = _____ 35 + 23 = _____ 27 + 42 = _____ 56 + 41 = _____ 88 73 58 69 97
- 4. 4 3 6 1 7 5 + 2 1 + 1 7 + 2 2 4 1 6 0 3 4 + 1 8 + 2 7 + 2 2 Model: 5 3 + 3 3 Steps: 1.3 + 3 write answer for ones 2.3 + 5 write answer for tens 3.the answer is 86 68 46 87 79 95 78 65
- 5. Model: 60 - 30 = Steps: 1.think 30 2.count difference by tens … say 40, 50, 60 (3 fingers = 30) 3.the answer is 30 Practice: 60 - 10 = _____ 70 - 40 = _____ 50 - 30 = _____ 90 - 50 = _____ 30 50 30 20 40
- 6. Model: 53 - 32 = Steps: 1.Think 32 2.count difference of ones... think 32, count to 33 (1 finger = 1) 3.count difference of tens… think 33 count to 53 (2 fingers = 20) 4.the answer is 21 Practice: 62 + 11 = _____ 35 + 23 = _____ 27 + 42 = _____ 56 + 41 = _____ 21 73 58 69 97
- 7. 4 3 7 7 7 5 - 2 3 - 1 2 - 2 4 4 8 6 7 7 7 - 2 1 - 3 0 - 2 4 Model: 5 3 - 3 3 Steps: 1.count difference of ones count from 3 to 3 = 0 write 0 under ones 2.count difference of tens, count from 3 to 5 = 2 write 2 under tens 3.the answer is 20 02 02 55 15 74 73 35
- 8. ∗ Ones before Tens ∗ Add by tens (if zeros are in the ones places) ∗ Add by ones then tens ∗ Count difference by tens (if zeros are in the ones places) ∗ Count difference by ones then tens ∗ Try mental math first ∗ Use algorythm last