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Chapter 8
Mastering Whole Number Operations
Addition and Multiplication involves all single digit addends and factors
Addend plus addend equals sum Factor times factor equals product How many basic facts are there????
Basic Facts
100!!!! For each addition and multiplication
How???
Basic Facts
1. Understand the meaning of the operations 2. Use thinking Strategies to Retrieve Facts *use facts that they know to figure out facts that they don’t i.e. 2+2 =4 so 2+3 must be one more than that * other stategies include counting on, counting back, skip counting, one more, one less…
Three Step Approach to Fact Mastery
3. Using Consolidating Activities for Drill and Practice games , activities , worksheets all help children memorize these facts
Three step approach cont…
Counting on … 6+3 start from the 6 and count on three times seven, eight , nine
Remind children to start from the larger # regardless of order of the problem ..3+6 still starting at 6 and add on three more
This method works well for both addition and subtraction
Sometimes a calendar works as a good visual to use this method—see next slide
Thinking Strategies for Addition and Subtraction
January 2012Sunday Monday Tuesday Wednesday Thursday Friday Saturday
1 New Year’s Day
2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 Martin Luther King Day
17 18 19 20 21
22 23 24 25 26 27 28
29 30
31
Use counters1. Show two groups of 62. “How much is 6+6?”3. Add one more to one of the groups4. Now we have 6 + 7. “How many
altogether?”5. One more than twelve6. Count out 13 objects with students7. 6+6 = 12 then 6 + 7 = 13
One more or one less
One addend is increased while the other addend is decreased by trying to make one addend 10
Use counters to model two piles 8 + 4=? Manipulate counters so one pile has 10 Now solve
Compensation
Order doesn’t matter 3+5 = 5+3
3•5 = 5•3However this does not work for Subtraction and Division6-4 ≠ 4-624/6 ≠6/24
Commutative Property of Addition and Multiplication
4 7 17 37 33 13 53 59 89
Calculator Game
John’s calculator is broken. The number 4 key will not work. How may possible combinations can you come up with on the screen to get 4 without actually using 4?
John has a math problem for hw and he is still trying to use the same calculator to solve this problem 24-4= ? Can you help him rewrite this problem so he can use his calculator?
Calculator/ broken calculator