Check your understanding

• What is 2.45 − 0.37?

• What is 4 – 3.78?

• What is 1.33 + 0.4?

Subtracting Across Zeroes

• If you have several zeroes in a row, and you need to borrow, go to the first digit that is not zero, and borrow.

• All middle zeroes become 9’s.• The final zero becomes 10.

Example: 15 – 9.372

159.372-

.0004 9 9 10

826.6

0 1

5

Subtracting Decimals

Use the grid below

What addition problem is modeled by the following grid?

A. 1.5 + 0.15 = 1.65 B. 1.45 + 0.2 = 1.65 C. 1.25 + 0.4 = 1.65 D. 1.2 + 0.45 = 1.65

What subtraction problem is modeled by the following grid?

A. 1.57 − 0.33 = 1.24 B. 1.9 − 0.33 = 1.57 C. 1.9 − 0.37 = 1.53 D. 2 − 0.1 = 1.9

Write sentences for the sum of 0.06 and 0.04 using numbers and then using words.

Numbers: _______ + _______ = _______ Words: _____ hundredths + ______ hundredths = _______ hundredths

________ hundredths + ________ hundredths = ______ tenth(s)

How many hundredths are in one tenth?

Multiplying Decimals

Step 1:

Multiply as if the factors were

whole numbers

Step 1: 8.5X2.54 2 5

1 7 0 0 2 1 2 5 next…..

Step 2:

Count the total decimals places

in the factors

Step 1: 8.5

X2.5 4 2 5

1 7 0 0 2 1 2 5 next…..

Step 3:

Give the product the total

decimal places of the factors

Step 1: 8.5

X2.5 4 2 5

1 7 0 0 2 1 .2 5

Try These:

1. 4.8 2. 3.55 x 0.5 x .05

Answers: 1. 4.8 2. 3.55

x 0.5 x .05

= 2.40 = 0.1775

Review Multiplying decimals

1. 0.403 x 5 =2. 524 x .05 = 3. .15 x 0.31 =.0465

2.015

Check your understanding

• You are multiplying 9.876 x 5.4321 . How many decimal places does the answer have?

• A student says 19.8 x 3.1=612.8. Is this anwer correct? Explain how you know

Word Problem using decimals

A year in Mars is 1.88 times as long as a year on Earth. An Earth year last 365.3 days. Find the length of year on Mars.

686.764 days

Word Problems

David and Dora are close friends studying in the same school. David’s home is 6.87 miles away from school. Dora’s home is 7 times as far as David’s home from school. Find the distance between Dora’s school and her home.

48.09 miles