Multiplying Decimals

Multiplying Decimals

Review of Module 1 Lesson 11 and 12

Multiplying- Key Words

• Product

• Times

• Copies

• As many as

• Doubled

• Tripled

• Of

Poll

How comfortable are you with multiplying decimals?

• Very Comfortable

• Comfortable

• Somewhat Comfortable

• I do not understand how to multiply decimals.

When multiplying decimals the order of numbers does not matter. This is called Communicative Property of Multiplication.

Multiplying Decimals - Step 1

Line up the numbers. TIP- Longer number on top, smaller on bottom.

Step 2- Multiply

Multiply the numbers without worrying abut the decimal, just yet.

Step 3- Place the decimal in the correct place.

The decimal in your answer should have the same amount of numbers as in the questions.

Poll

Did you understand the steps to multiplying decimals?

• YES

• NO

Lets practice!

Work out each of the problems on a separate sheet of paper and choose final answer on the slide.

Multiple Choice

2 copies of 4 tenths

• 0.8

• 0.4

• 80

• 4

Multiple Choice

3 times 5 hundredths

• 500

• 1500

• 1.5

• .15

Multiple Choice

Anna buys groceries for her family. Hamburger meat is $3.38 per pound, sweet potatoes are $0.79 each, and hamburger rolls are $2.30 a bag. If Anna buys 3 pounds of meat, 5 sweet potatoes, and one bag of hamburger rolls, what will she pay in all for the groceries?

• $10.14

• $3.95

• $2.30

• $16.39

Multiple Choice

9 times as much as 7 tenths

• 0.7

• 0.9

• 6.3

• 63

Poll

How are you feeling so far about multiplying decimals?

• Still Confused

• Frustrated

• Better

• Awesome

Let's work on estimating the products.

Remember that "Estimate" means approximate or close to. Opposite of EXACT!

Step 1- Look at your problem

Look at the problem you are working with.

Step 2. Identify your wholes

Identify the whole numbers in each or round to the nearest whole and multiply your wholes.

Step 3- Estimate the answer.

Once you have multiplied the wholes, estimate the total to your problem by looking at the closest number to your estimate. Ex. 24 is closest to 25.36 therefore, 25.36 is the actual answer to this problem.

Let's practice!

Work out the problems on a separate sheet of paper and choose your final answer on the slide.

Open Ended

In 2.1 x 3, what two numbers represent your whole?

Multiple Choice

What is a reasonable product for 2.1 x 3

• 0.63

• 6.3

• 63

• 630

Multiple Choice

What is a reasonable product for 4.27 x 6=

• 2562

• 2.562

• 25.62

• 256.2

Open Ended

How do you know?

Multiple Choice

What is a reasonable product for 7 x 6.053=

• 4237.1

• 4.2371

• 42.371

• 42371

Open Ended

How do you know?

Multiple Choice

Yi Ting weights 8.3 kg. Her older brother is 4 times as heavy as Yi Ting. How much does her older brother weight?

• 24kg

• 33.2 kg

• 12.3kg

• 332 kg

Multiple Choice

Tim is painting his storage shed. He buys 4 gallons of white paint and 3 gallons of blue paint. Each gallon of white paint costs $15.72 and each gallon of blue paint costs $21.78. How much money will Tim spend in all on paint.

• $37.50

• $62.88

• $128.22

• 65.38