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Mental Math Strategies for Grade 3
- 1. Mental Math Strategies for Grade 3 Students All photos Courtesy of MS Clip Art Roshel Salvador
- 2. What is MentalMath??
- 3. It’s the abilityto solve math equations in your head….
- 4. WITHOUT using paper OR a pencil!
- 5. With Mental Math you can manipulate (change) your number to make an easier equation. What’s an equation??? It’s the number sentence.
- 6. Here are afew Mental Math strategies: • Count on • Doubles • Near Doubles • Make a Friendly Number • Front-End Adding or Expanded Notation
- 7. Count On: Ifone of the numbers being added is a small number, then just count on.
- 8. Count On: 7+3= 3 is a small number, so just count on to get your answer.
- 9. Count On: RULE: Usually, if one of the numbers are from 1 to 5, you can just count on.
- 10. Doubles: Knowing your doubles can help you solve equations quickly!
- 11. Doubles: Doublesare when you take a number and add it to itself. Eg. 2+2= 9+9= 15+15= 25+25= You double the number.
- 12. Near Doubles: Knowing your doubles helps with the Near Doubles strategy
- 13. Near Doubles: NearDoubles almost looks like a double, but it is off by 1,2,3 or 4 Near Double 2 + 2+1 Doubles Doubles
- 14. Near Doubles: Examples ofother near doubles: 11+13= 5+8= 11 + 11+2= 5 + 5+3
- 15. Near Doubles: You can even use subtraction for near doubles. 11+13= 5+8= 13-2 + 13 8-3 + 8 8+8 - 3 13+13 - 2
- 16. Make a FriendlyNumber: What is a friendly number???
- 17. Make a FriendlyNumber: A friendly number is a number that ends with a “0”. Numbers with a “0” in the ones spot are easier to add with
- 18. Make a FriendlyNumber: For example, to make 28 a friendly number, I can add 2 to it to make it 30
- 19. Make a FriendlyNumber: More examples: • Add 5 to 35, to make 40 • Subtract 2 from 22 to make 20
- 20. Make a FriendlyNumber: This is how it helps: 9 + 4= If I make 9 into a 10, 10 + 3= it is easier to solve because I’m working with a friendly number.
- 21. Make a FriendlyNumber: BUT…. Notice how I changed the equation to 10 + 3, NOT 10 + 4 I had to manipulate the equation. Otherwise, I’m just make a new and different equation that won’t give the same answer
- 22. Make a FriendlyNumber: In adding, it is called “give and take”. If you give to one side, you have to take from the other side. 9 + 4= 13 (give 1) +1 -1 (take 1) 10 + 3= 13 New equation
- 23. Make a FriendlyNumber: In subtracting, it is called “give/give” or “take/take”. If you give to one side, you have to give to the other side. If you take from one side, you have to take from the other side.
- 24. Make a FriendlyNumber: Some examples of “give/give” and “take/take”: 9 – 4= 5 (give 1) +1 +1 (give 1) 10 – 5= 5 New equation 11 – 4= 7 (take 1) -1 -1 (take 1) 10 – 3= 7 New equation
- 25. Make a FriendlyNumber: When you: • “give & take” adding • “give/give” subtracting • “take/take” subtracting You are compensating!
- 26. Front-End Adding When you front-end add you use expanded notation or your place values.
- 27. Front-End Adding Expanded Notationis breaking your number into ones, tens and hundreds Eg. 58 42 5 tens, 8 ones 4 tens, 2 ones 50 + 8 40 + 2
- 28. Front-End Adding • Front-endadding is when you start adding from the left and move to the right Eg. 34 + 45 - start with the tens: 30 + 40 = 70 - now the ones: 4 + 5 = 9 Now you`re working with a friendly number 70 + 9 = 79
- 29. Let’s Review theMental Math Strategies • Count on • Doubles • Near Doubles • Make a Friendly Number • Front-End Adding or Expanded Notation