1. Multiplying Decimals and Circumference of a Circle
Section 5.3
Multiplying Decimals and Circumference of a Circle

2. Multiplying Decimals Steps
Count the number of places after the decimal for each number (a, b), and add together (a + b = c)
Drop decimal
Multiply the two numbers together.
Put decimal at the end of the number and move the decimal to the left C places.

3. Example
Simplify (0.15)( 1.25)

4. Example
Simplify x 58.12

5. 10’s Multiplying Decimals by Powers of 10
Such as 10, 100, 1,000, 10,000
Move the decimal point to the right the same number of places as there are zeros in the power of 10
10 :move the decimal to the right 1 place
100 : move the decimal to the right 2 places
1,000 : move the decimal to the right 3 places
10,000 : move the decimal to the right 4 places.

6. Example
Simplify * 100

7. Example
Simplify * 1000

8. 10’s Multiplying Decimals by Powers of 10
Such as 0.1, 0.01, 0.001, , etc
Move the decimal point to the left the same number of places as there are decimal places in the power of 10
0.1 : move the decimal to the left 1 places
: move the decimal to the left 2 places
0.001 : move the decimal to the left 3 places.
: move the decimal to the left 4 places.

9. Example
Simplify * 0.1

10. Example
Simplify 459 * 0.01

11. Circumference
C = 2πr
C = πd
π = 22/7 or π = 3.14

12. Example
Find the circumference. Let π = 22/7

13. Example
Find the circumference. Let π = 3.14

14. Example
The London Eye, built for the millennium celebrations in London, resembles a gigantic Ferris wheel with a diameter of 135 meters. If Adam Hawn rides the Eye for one revolution, find how far he travels. Given an exact answer and an approximation using 3.14 for pi.