Brainstorming about Area - Tuesday Oct 19, 2010

Today we brainstormed ways to calculate the area of a circle. Ms. Gesner was very impressed by the depth of the thinking.

Ways to calculate area of a circle

1. Use the formula. A = ∏ r^2 (Area equals pi times the radius squared. Area equals pi times radius, times radius)

2. Use gridpaper.

3. Use the "Egyptian method"

Here is one way to do it (There are several similar methods).

Draw a square around the circle with sides equal to the diameter

Divide the circle into 9 equal squares

Connect the dots to draw an octagon

Calculate the area of the octagon.

4. Use the Lucas pizza pie triangle method.

Divide the circle into 8 slices.

Use the formula for area of a triangle (A = b x h /2) to caculate the area of each slice

5. Use the "lazy parallelogram" method.

Cut the circle into 8 slices. Make a parallelogram. The area of a parallelogram = b x h (not side times side... you must use the height of the parallelogram)

Homework:Finish all examples on sheet "4.3 Circumference of a Circle"

vendredi le 15 octobre

Today we discussed - If we know the Circumference how can we go backwards to find the diameter?

USING DIVISION!

C=pi x d so d = C/pi

(in words, Circumference equals pi times the Diameter. The Diameter is Circumference divided by pi.)

Next we finished comparing diameter and circumference using yarn.

Homework: - Do all even questions on sheet "3.4 Circumference". Do the maze and pizza examples on the back. This is due Tuesday because Monday is Day 8, no Math Class :-(

Have a nice weekend!.

Thurs - Mini-Quiz & more circles

As a warm-up we looked at XZY + XYZ = YZX. X must be less than 5, Y must be at least double X. X=4 Y=9 Z=5
We did a short quiz on circles.
We corrected the odd numbers of the circle questions.

HW - Finish all questions on the circles page.

Tuesday & Wednesday

Tuesday - We used yarn to explore the ratio between diameter and circumference of a circle.

Wednesday - In the lab we finished the Geometer's Sketchpad lab. In class we did "Circumference of a Circle" worksheet.

HW - Do all odd examples on both sides of the circle sheet. QUIZ TOMORROW - Know how to label the radius, diameter & circumference.

Friday - Geometer's Skektchpad!

Today we reviewed the terms diameter, radius and chord.

We then came down to the lab to use the fabulous programme GEOMETER'S SKETCHPAD.

Homework:

Bring a Geometry set, amke sure test was signed and have a happy Thanksgiving.

Wednesday, Thursday - Square Roots and Circles

On Wednesday we looked at how to approximate the value of a square root.

Homework: Do #18-22 on Square Roots sheet.

On Thursday we discussed circles - What makes them unique? - What makes them hard to draw freehand?

We watched a video on freehand circles:

http://www.youtube.com/watch?v=eAhfZUZiwSE

Radius -

Diameter -

Circumference -

Monday Oct 4th - a quiet class

Today some students were finishing Test #1.
The other students worked quietly on the puzzle sheet, or on doing all examples on sheets where only odd or even numbers were assigned.

Homework for Tuesday:
"Chapter 3 Pretest Sheet" Do all examples in Column a (Do 1a, 2a, 3a, 4a, 5a, 6a)

How to multiply decimals:
http://www.youtube.com/watch?v=zEHbLRHxQpE