Multiply with decimals

Standard UW.GAP.5.M.NBT.07 Add, subtract, multiply, and divide decimals to hundredths using concrete models or drawing and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

Essential Questions1. What is addition? How do you add decimals?

2. What is subtraction? How do you subtract decimals?

3. What is multiplication? How do you use a model and partial products to represent multiplying decimals?

4. What is division? How do you use a model and partial products to represent dividing decimals?

Set....

Think about the strategies we use to multiply whole numbers....

Take turns with your face partner and describe how we multiply and divide whole numbers.

Objective: I can multiply decimals to hundredths place.

Decimal - a number with a fraction of tenths, hundredths, etc. written after a decimal point.

Decimal point - the (.) between a whole number and fractions of tenths, hundredths, thousandths, etc.

Digit- any of the numerals 0-9, which may be part of a larger number.

24.56 x 4 . 1 = 100.696

Let’s Review

Think back to Adding and Subtracting

DecimalsStep 1- line up the decimals

Step 2- add any place holding zeros

Step 3 - add or subtract like you always do

Step 4 - bring the decimal straight down

Multiplication is much different, let’s learn how...

Rules for Multiplying Decimals

When multiplying decimals, multiply just like normal then

move decimal over to the right, then move decimal that many

place in answer to the left.

Multiplying DecimalsExample 1

Solve = 10.7 x 0.13 10.7 1 decimal place

Example 1Solve = 10.7 x 0.13

10.7x0.13

1 decimal place2 decimal places

Multiplying Decimals

Example 1Solve = 10.7 x 0.13

10.7x0.13 321

1 decimal place2 decimal places

Multiplying Decimals

Example 1Solve = 10.7 x 0.13

10.7x0.13 321 1070

1 decimal place2 decimal places

Multiplying Decimals

Example 1Solve = 10.7 x 0.13

10.7x0.13 321

+1070 1.391

1 decimal place2 decimal places

3 decimal places

Multiplying Decimals

Let’s watch how to multiply with models

http://www.slideshare.net/slideshow/embed_code/9425239

Let’s try one together...

4.56 x .83

Now you try

16.73 x 4.89

Closure

Think about what is different about multiplying whole numbers and multiplying decimals

On your slate: Write a $2 summary explaining what is different

Repeat todays objective

Independent Practice1. 45.2 x 2.3=

2. 98.01 x 7=

3. 6.6 x 4.9

4. 39.4 x 23.09=

5. 6.34 x 23 =

6. 10.6 x 15.3=

7. 99.23 x 34=

8. 7.34 x 2.34=