2.8 Multiplication of Whole Numbers and

Decimals

Tuesday, September 24th

In your math notebook, title the page 2.8, answer the following question.

Estimate the solution to this problem. Write a number sentences showing you found your estimate:

3.7 * 6.2=?Show your work!

Partial Products Method 236*4100s 10s 1s

Think of 236 as 200+30+6 2 36

Multiply each part of 236 by 4 x 4

4 * 200 8 0 04* 30 1 2 04*6 + 2 4

Add all 3 partial products. 9 44

Partial Products Method continued 43*26100s 10s 1s

Think of 26 as 20+6 2 6Think of 43 as 40+3 x 4 3

Multiply each part of 26 20*40 8 0 0 by each part of 43 40*6 2 4 0

3*20 6 03*6 + 1 8

Add the 4 partial products. 1,1 1 8

43*26 = 1,118

Multiplication of DecimalsOne way to solve multiplication containing decimals factors is to

multiply as though both factors were whole numbers and then adjust the product. Specifically:

1. First make a magnitude estimate of the product. 2. Multiply the numbers as though they were whole numbers.3. Then use the magnitude estimate as a guide to inserting the

decimal point at the correct location in the answer.

For example: 1.3 * 51. Make a magnitude estimate: 1.3 rounds to 1; because 1 *5 =5, the

product will be in the ones. 2. Ignore the decimal point and mulitply 13 *5 as though both factors

were whole numbers: 13*5 = 65.3. Since the magnitude estimate is in the ones, the product must be in

the ones. Answer must be 6.5. 1.3 *5= 6.5

• Watch the following video for extra review!– If you the link does not work from the PowerPoint,

copy and paste the link!

– http://everydaymath.uchicago.edu/teaching-topics/computation/mult-part-prod/

2.9 The Lattice Method of Multiplication

Wednesday, September 25th

Lattice MethodBegin with the diagonal in the bottom right-hand corner. The

diagonal lines outside of the lattice squares are the answer spaces.

42*37 = ?1. Write 37 above the lattice. 3 7

Write 42 on the right side. 42. Multiply 4*7. Then multiply 4*3.Multiply 2*7. Then multiply 2*3.Write the answers as shown. 23. Add the numbers along eachDiagonal. Begin with the diagonalIn the bottom right-hand corner. The sum of the numbers in the 3 7Second diagonal is 15, so write 1 above 42 in the third diagonal. The sum of the Numbers in that diagonal is 1+2+2=5 2

4. Answer is shown starting on the upper left side of the lattice and continuing below the lattice.

In class we will work on multiplying whole numbers and decimals using the lattice method!

But before then, try it out on your own!

In your math notebook, title the page 2.9, answer the following question using the lattice method. 3.7 * 4.2

Show work!

• Watch the following video for extra review!– If you the link does not work from the PowerPoint,

copy and paste the link!

• http://everydaymath.uchicago.edu/teaching-topics/computation/mult-lattice/

2.10 Comparing Millions, Billions, and Trillions

Thursday, September 26th

In your math notebook, title the page 2.10, answer the following question.

1. Explain the strategy you would use to find the number of minutes in one year.

Show your work!

What is 1,000 times 1 million? 1 billion (1,000,000,000)

1,000,000,000 = 1,000 *1,000,000

One billion has what relationship to 1 trillion? One trillion (1,000,000,000,000) is 1,000 time 1 billion.

1,000,000,000,000 = 1,000 * 1,000,000,000

** Count the number of zeros!

What’s the difference between a guess and an estimate?

Guess= an opinion that you might state without the support of other information.

Estimate= based on some knowledge about the subject and is often called an educated guess.

Friday, September 27th

Unit 2 Review

Study the following skills:1. Add and subtract whole numbers and decimals. 2. Convert between U.S. customary units of length.3. Identify the place value in digits. 4. Identify multiplication errors5. Make magnitude estimates.6. Explain usefulness of making an estimate. 7. Describe probabilities using words or phrases.8. Write numbers in expanded notation. 9. Find the landmarks for a data set.

Use your SRB, Math journal pages, PowerPoint slides, study links, notes to help you study for the assessment on Monday, September 30th.