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# Operations and Whole Numbers: Developing Meaning - PowerPoint PPT Presentation

Operations and Whole Numbers: Developing Meaning. Model by beginning with word problems. Real-world setting or problem. Models Concrete Pictorial Mental Language. Mathematical World (symbols). Understanding Addition and Subtraction.

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Operations and Whole Numbers: Developing Meaning

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#### Presentation Transcript

• Model by beginning with word problems

Real-world setting or problem

Models

Concrete

Pictorial

Mental

Language

Mathematical World

(symbols)

• There are four types of addition and subtraction problems

• Joinaction

• Separateaction

• Part-part-whole relationships of quantities

• Comparerelationships of quantities

• Join

Result Unknown

Change Unknown

Start Unknown

Result Unknown

Change Unknown

Start Unknown

Whole Unknown

Part Unknown

Peter has 11 cookies. Four are chocolate chip cookies and the rest are peanut butter cookies. How many peanut butter cookies does Peter have?

Difference Unknown

• Peter has 11 cookies and Erika has 7 cookies. How many more cookies does Peter have than Erika?

Larger Unknown

Erika has 7 cookies. Peter has 4 more cookies than Erika. How many cookies does Peter have?

Smaller Unknown

Peter has 11 cookies. Peter has 4 more cookies than Erika. How many cookies does Erika have?

• Direct modeling refers to the process of children using concrete materials to exactly represent the problem as it is written.

• Join and Separate (problems involving action) work best with Direct Modeling

• Meghan has some cookies. Four are chocolate chip cookies and 7 are peanut butter cookies. How many cookies does Meghan have? (part-part-whole)

• Once the children have had many experiences modeling and talking about real life problems, the teacher should encourage children to write mathematical symbols for problems.

• A number sentence could look like this

• 2 + 5 = ? Or 2 + ? =7

• The Partial-Sums Method is used to find sums mentally or with paper and pencil.

• The Column-Addition Method can be used to find sums with paper and pencil, but is not a good method for finding sums mentally.

• The Short Method adds one column from right to left without displaying the partial sums(the way most adults learned how to add)

• The Opposite-Change Rule can be used to subtract a number from one addend, and add the same number to the other addend, the sum is the same.

• Example: 348 + 177=?

• 100s 10s1s

• 3 48

• +1 7 7

• 4 0 0 Add the 100s (300 + 100)

• 1 1 0 Add the 10s (40 + 70)

• 1 5 Add the 1s ( 8 + 7)

• 5 2 5 Add the partial sums (400+110+15)

• Example: 359 + 298=?

• 100s 10s 1s

• 3 5 9

• +2 9 8

• 5 14 17 Add the numbers in each column

• 5 15 7 Adjust the 1s and 10s: 17 ones = 1 ten and 7 ones

• Trade the 1 ten into the tens column.

• 6 5 7 Adjust the 10s and 100s: 15 tens = 1 hundred and 5 tens. Trade the 1 hundred into the hundreds column.

• 248 + 187=?

• 1 1

• 2 4 8

• + 1 8 7

• 4 3 5

• 8 ones + 7 ones = 15 ones = 1 ten + 5 ones

• 1 ten + 4 tens + 8 tens = 13 tens = 1 hundred + 3 tens

• 1 hundred + 2 hundreds + 1 hundred = 4 hundreds

• In 8 + 4 = 12, the numbers 8 and 4 are addends.

• If you subtract a number from one addend, and add the same number to the other addend, the sum is the same. You can use this rule to make a problem easier by changing either of the addends to a number that has zero in the ones place.

• One way: Add and subtract

• +26 (subtract 1) +25

• 85

• Another way. Subtract and add 4.

• 59 (subtract 4) 55

• + 26 (add 4) + 30

• 85

• The Trade-First Subtraction Method is similar to the method that most adults were taught

• Left-to-Right Subtraction Method

• Partial-Differences Method

• Same-Change Rule

• If each digit in the top number is greater than or equal to the digit below it , subtract separately in each column.

• If any digit in the top number is less than the digit below it, adjust the top number before doing any subtracting. Adjust the top number by “trading”

• Subtract 275 from 463 using the trade-first method

• 100s 10s 1s

• 4 6 3

• - 2 7 5

• Look at the 1s place. You cannot subtract 5 ones from 3 ones

• 100s 10s 1s Subtract 463 - 275

• 5 13

• 4 6 3

• - 2 7 5

• So trade 1 ten for ten ones. Look at the tens place. You cannot remove 7 tens from 5 tens.

• Subtract 463 – 275

• 100s 10s 1s

• 15

• 3 5 13

• 4 6 3

• - 2 7 5

• 1 8 8

• So trade 1 hundred for 10 tens. Now subtract in each column.

• Starting at the left, subtract column by column.

• 9 3 2

• - 3 5 6

• Subtract the 100s 932

• - 300

• Subtract the 10s 632

• - 50

• Subtract the 1s 582

• - 6

• 576

• Subtract from left to right, one column at a time. Always subtract the larger number from the smaller number.

• If the smaller number is on the bottom, the difference is added to the answer.

• If the smaller number is on top, the difference is subtracted from the number.

• 8 4 6

• - 3 6 3

• Subtract the 100s 800 – 300 +5 0 0

• Subtract the 10s 60 – 40 - 2 0

• Subtract the 1s 6 - 3 + 3

4 8 3

• 92 –36 = ?

• - 36 (add 4) – 40

• 56

• Another way subtract 6

• 92 (subtract 6) 86

• - 36 (subtract 6) - 30

• 56

• Partial-Products Methods

• Lattice Method

• You must keep track of the place value of each digit. Write 1s 10s 100s above the columns.

• 4 * 236 = ?

• Think of 236 as 200 + 30 + 6

• Multiply each part of 236 by 4

• 4 * 236 = ? 100s 10s 1s

• 2 3 6

• * 4

• 4 * 200 8 0 0

• 4 * 30 1 2 0

• 4 * 6 0 2 4

• Add these three 9 4 4

• partial products

• 6 * 815 = ?

• The box with cells and diagonals is called a lattice.

• 8 1 5

6

• Equal Grouping

• Partitive Division – Size of group is unknown

• Example:

• Twenty four apples need to be placed into eight paper bags. How many apples will you put in each bag if you want the same number in each bag?

• Rate

• Partitive Divison – size of group is unknown

• Example:

• On the Mitchell’s trip to NYC, they drove 400 miles and used 12 gallons of gasoline. How many miles per gallon did they average?

• Number of equal groups is unknown

• Quotative Division

• Example:

• I have 24 apples. How many paper bags will I be able to fill if I put 3 apples in each bag?

• Number of equal groups is unknown

• Quotative Division

• Example:

• Jasmine spent \$100 on some new CDs. Each CD cost \$20. How many did she buy?

• The Partial Quotients Method, the Everyday Mathematics focus algorithm for division, might be described as successive approximation. It is suggested that a pupil will find it helpful to prepare first a table of some easy multiples of the divisor; say twice and five times the divisor. Then we work up towards the answer from below. In the example at right, 1220 divided by 16, we may have made a note first that 2*16=32 and 5*16=80. Then we work up towards 1220. 50*16=800 subtract from 1220, leaves 420; 20*16=320; etc..