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Do Now Solve the problems in the most efficient way you can. 3 + 8 = ____ 10 – 7 = ____ 6 + 3 + 4 = ____ 18 – 9 = ____ 36 + 22 = ____ 84 – 40 = ____ Addition and Subtraction Strategies in First Grade How to Become a More Efficient Mathematician 1st Grade Expectations • Master a number of different addition/subtraction strategies. • Choose the strategies that work best for him/her and for the particular problem. • Be flexible with strategies and choose ones that are efficient. • Check work with another strategy. Full Model Prompt: How can you use a picture to solve this problem? • Drawing all for addition Counting objects, counting on fingers, drawing a picture • Crossing off for subtraction Taking away objects, taking away fingers, crossing off in a picture Counting On/Counting Back Prompt: How can you use a number line and/or counting to solve this problem? • Adding and subtracting are like counting up and back • Start with the larger number and count on or back (“hop”/”jump” forward or back) • Efficient strategy for solving single-digit addition and subtraction problems • Show your work with a number line or drawing Examples: 3 + 8 = ___ 8 – 2 = ___ Using Facts We Know (Fluency) Prompt: How can you use facts you know to solve this problem? • Combinations of 10 6 + 3 + 4 = ____ I know 6 + 4 = 10 and 10 + 3 = 13 • Doubles and Near Doubles 8 + 7 = _____ I know 7 + 7 = 14, so one more is 15 • Fact Families – using what we know about addition to help with subtraction 10 – 7 = ____ I know 7 + 3 = 10, so 10 – 7 = 3 Keep One/Break One Prompt: How can you break a number into helpful parts to solve this problem? • Break one number into two parts so that you can make a landmark number (e.g., 10 or a multiple of 10) 9 + 7 = ____ 18 – 9 = ____ 36 + 8 = ____ Using Place Value Prompt: How can you use what you know about 10s and 1s to solve this problem? 36 + 22 = ____ • Base 10 Model: Using or drawing base 10 blocks • Expanded Form: Breaking numbers into 10s &1s 30 + 6 20 + 2 50 + 8 = 58 • Keep One/Break One: Adding multiples of 10 first 36 + 20 = 56 56 + 2 = 58