The circle and area

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 1

Welcome to maths

Need: 

• Book open on p. 127 (you can start with exercise 51)
• Notebook open on an empty page (with a margin)
• Pen 
• Pencil (+sharpener and eraser)
• Geo triangle
• Calculator

 Did you check your homework?

Yes? Continue with ex. 51, 52 and 53 on p. 127

No? First check and correct your homework

Remember the difference between radius and diameter?

Radius

From the centre to the outside of the circle, so 0.5*diameter

Diameter

Line from one side of a circle to the other side through the centre, so the diameter is 2*radius

Goal

• To calculate the area of a circle
• Write down calculations in a short and formal way
• Check your work 

How do you calculate the radius
when you know the circumference?

Calculate the perimeter of a circle in cm with a diameter of 10 dm.

circumference=π⋅diameter

C=2πr

area=π⋅radius​2​​

A=πr​2​​

Calculate the radius of a circle with an area of

49π

Calculate the diameter of the circle with an area of

25π

Calculate the radius of a circle with a circumference of

6π

Calculate the area of the coloured part of the circles.

Answer like this --> 9pi / 36pi. 

Share at least one out of two answers.

Work on...

• exercises 51, 52, 53 and 54 on p. 127
• Check your work after 8 minutes with a different colour
• Copy HW in your planner
• HW: Do ex. 51, 52, 53 and 54 on p. 127

Next lesson

• You have finished and checked your homework 
• HW: Do ex. 51, 52, 53 and 54 on p. 127 + uploads LessonUp
• We will work on volume