Do Now #41 11/13/14

Jim wants to tile his shower wall. The wall is 7.5 feet tall and 4.5 feet wide. ◦ 1) What is the area of the wall?◦ 2) If the tiles cost $1.50 per square foot, how

much will it cost to tile the whole wall?

Do Now #41 11/13/14

Homework Review/Dipstick Quiz

Chapter 3B Extension

Parts of a Circle

Parts of a Circle

.Radius

Center

Circumference(outside)

Diameter

The distance across a circle passing through the centerA diameter cuts the circle exactly in

half

DIAMETER - Definition

The distance from the center of a circle to any point in the circumference

Plural Form: Radii2 Radii = 1 diameter

RADIUS - Definition

The center point of a circleCENTER - Definition

.

The distance around the circle

There are 2 formulas used to find the circumference of a circle

C = ∏d OR C =2∏r

CIRCUMFERENCE - Definition

∏ ≈ 3.14• Pi (∏) is pronounced like the word pie• ∏ is the 16th letter of the alphabet• ∏ is an irrational number (never ending and no digits repeat)

• ∏ can be expressed as a fraction• Math Holiday - PI DAY

Anyone Guess the Date???

∏ Facts

722

3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067…

Here are the 1st 100 digits of PI

You could find the circumference of a circle given EITHER the diameter OR the radius

Finding Circumference

Circumference FormulasGIVEN THE DIAMETER

C = ∏d

C = 3.14 x diameter

GIVEN THE RADIUS

C = 2∏r

C = 2 x 3.14 x radius OR

C = 6.28 x radius

Given Diamter Example 1

Given Diameter Example 2

When given the RADIUS of the circle you must use

C = 2∏r to find the circumference of the circle

because doubling the radius gives you the diameter.

Remember…

Given Radius Example 1

Given Radius Example 2

#1 Find the Circumference

You Try In Your Notebook…

You Try In Your Notebook…

6.2 in

#2 Find the Circumference

Master Pizza in Union offers large pizzas that have a diameter of 12 inches and medium pizzas that have a diameter of 8.5 inches. What is the difference in circumference between the two pizza sizes?

Word Problem #1 – Critical Thinking

The circular runners path in New York’s Central Park has a radius of 1.25 miles. What is the distance around the entire runners path?

If Lauren can jog one mile in 9 minutes, how long will it take her to jog the entire path?

Word Problem #2 – Critical Thinking