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Developing Strategies for Addition and Subtraction

Developing Strategies for Addition and Subtraction. 2 nd Grade Matt Rinehart. Drawbacks to Memorizing Facts. Inefficient – There are too many facts to memorize. Inappropriate applications – Students don’t check their work and misapply the facts.

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Developing Strategies for Addition and Subtraction

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  1. Developing Strategies for Addition and Subtraction 2nd Grade Matt Rinehart

  2. Drawbacks to Memorizing Facts • Inefficient – There are too many facts to memorize. • Inappropriate applications – Students don’t check their work and misapply the facts. • Inflexible – Students don’t learn flexible strategies and therefore continue to use counting.

  3. Reasoning Strategiesfor Addition Facts There are 100 basic addition facts.

  4. Adding Zero 3 frogs were in a pond, one hour later no frogs had joined them. How many frogs are in the pond? 3+0=3 Covers 19 facts

  5. One More Than and Two More Than There were 7 flowers in the vase on the kitchen table. Mother added 2 more. How many flowers are in the vase? 7+2=9 Covers 36 facts

  6. Using 5 as an Anchor 6 is 5+1 7 is 5+2 6+7 is 5+5+ “extras” 1 & 2 There are 6 red lollipops and 7 blue lollipops. How many total lollipops are there?

  7. 10 Facts • Use ten-frame cards to help students understand and master the number combinations that make 10. • Helps with basic fact mastery. • Foundation for addition with larger numbers. • Promotes understanding of place value concept.

  8. Up Over 10 8+6=? 8 is 2 away from 10 Take 2 from 6 to make 10 Then add remaining 4 to get 14 Extremely important strategy. Heavily used in high performing countries Covers 36 facts

  9. Doubles • Easy for students to learn, or already know. • Possibly due to rhythmic nature. Covers 10 facts 2+2 5+5 9+9 4+4 6+6

  10. Near Doubles Doubles plus one or Doubles minus one 8+7 5+4 6+7Covers 18 facts

  11. Reasoning Strategiesfor Subtraction Facts There are 100 basic subtraction facts.

  12. Subtraction as Think-Addition • Students need to have a strong grasp of additions facts • Students need to understand missing part and part-part-whole concepts student sees 7-3=? student thinks 3 plus what makes 7.

  13. Joe had 3 cookies. His brother gave him some more. Now he has 7 cookies. How many cookies did his brother give him? 7-3=? 3+?=7

  14. Down Over 10 or Take From the 10 14-9=? I know 14 is 10+4 I know 10-9=1 1 and 4 is 5 14-9=5

  15. Conclusions

  16. What Mr. Rinehart will not do. • use lengthy timed tests. • use public comparison. • require facts to be learned in order. • rush memorization.

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