1. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ Objective: to measure radius and diameter and discover their relationship.

2. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ Objective: to measure radius and diameter and discover their relationship. All points in a circle are the same distance from the centre. This distance is called the radius. Radius – the distance from the centre of a circle to the outside of the circle. radius

3. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ Objective: to measure radius and diameter and discover their relationship. All points in a circle are the same distance from the centre. This distance is called the radius. Radius – the distance from the centre of a circle to the outside of the circle. The longest line segment in any circle is the diameter. It always passes through the centre. Diameter – the distance across a circle directly Through the centre. radius diameter

4. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ All points in a circle are the same distance from the centre. This distance is called the radius. Radius – the distance from the centre of a circle to the outside of the circle. The longest line segment in any circle is the diameter. It always passes through the centre. Diameter – the distance across a circle directly Through the centre. The radius is always ½ the diameter & the diameter is always 2 times the radius. d = diameter & r = radius So, r = d /2 and d = 2 x r or d = 2r. radius diameter

5. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ What can you say about a circle with a radius of 5cm. and a circle with a diameter of 10 cm.?

6. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ What can you say about a circle with a radius of 5cm. and a circle with a diameter of 10 cm.? Radius = 5cm

7. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ What can you say about a circle with a radius of 5cm. and a circle with a diameter of 10 cm.? Both circles are exactly the same! They are __________? Radius = 5cm Diameter = 10cm

8. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ What can you say about a circle with a radius of 5cm. and a circle with a diameter of 10 cm.? Both circles are exactly the same! They are congruent! Radius = 5cm Diameter = 10cm

9. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6

10. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #2 - Draw a circle with each radius without using a compass. a) 7 cm b) 4 cm Label the radius, then find the diameter. Explain the method you used to draw the circles. What are the disadvantages of not using a compass?

11. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #2 - Draw a circle with each radius without using a compass. a) 7 cm b) 4 cm Label the radius, then find the diameter. Explain the method you used to draw the circles. What are the disadvantages of not using a compass? 7 cm.

12. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #2 - Draw a circle with each radius without using a compass. a) 7 cm b) 4 cm Label the radius, then find the diameter. Explain the method you used to draw the circles. What are the disadvantages of not using a compass? d = 2r, so d = 2 x 7cm = 14cm. 7 cm.

13. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #2 - Draw a circle with each radius without using a compass. a) 7 cm b) 4 cm Label the radius, then find the diameter. Explain the method you used to draw the circles. What are the disadvantages of not using a compass? d = 2r, so d = 2 x 7cm = 14cm. 7 cm. 4 cm.

14. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #2 - Draw a circle with each radius without using a compass. a) 7 cm b) 4 cm Label the radius, then find the diameter. Explain the method you used to draw the circles. What are the disadvantages of not using a compass? d = 2r, so d = 2 x 4cm = 8cm. d = 2r, so d = 2 x 7cm = 14cm. 7 cm. 4 cm.

15. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #2 - Draw a circle with each radius without using a compass. a) 7 cm b) 4 cm Label the radius, then find the diameter. Explain the method you used to draw the circles. What are the disadvantages of not using a compass? d = 2r, so d = 2 x 4cm = 8cm. d = 2r, so d = 2 x 7cm = 14cm. To draw the circles, I made a horizontal and verical diameter. Then arced from each point. If you don’t use a compass you are not as accurate. 7 cm. 4 cm.

16. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 3. a) A circle has diameter 3.8 cm. What is the radius? b) A circle has radius 7.5 cm. What is the diameter?

17. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 3. a) A circle has diameter 3.8 cm. What is the radius? r = d /2, So r = 3.8 cm / 2 = 1.9cm b) A circle has radius 7.5 cm. What is the diameter?

18. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 3. a) A circle has diameter 3.8 cm. What is the radius? r = d /2, So r = 3.8 cm / 2 = 1.9cm b) A circle has radius 7.5 cm. What is the diameter? d = 2r, So d = 7.5cm x 2 = 15cm

19. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #4) A circular tabletop is to be cut from a rectangular piece of wood that measures 1.20 m by 1.80 m. What is the radius of the largest tabletop that could be cut? Justify your answer. Include a sketch. 1.80m 1.20m

20. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #4) A circular tabletop is to be cut from a rectangular piece of wood that measures 1.20 m by 1.80 m. What is the radius of the largest tabletop that could be cut? Justify your answer. Include a sketch. The largest circle that can fit in this rectangle has a diameter of the smaller width = 1.20m. 1.80m 1.20m

21. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 #4) A circular tabletop is to be cut from a rectangular piece of wood that measures 1.20 m by 1.80 m. What is the radius of the largest tabletop that could be cut? Justify your answer. Include a sketch. The largest circle that can fit in this rectangle has a diameter of the smaller width = 1.20m. So… the radius is 1.20 / 2 = 0.6m 1.80m 1.20m 0.6m

22. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 6) A glass has a circular base with radius 3.5 cm. A rectangular tray has dimensions 40 cm by 25 cm. How many glasses will fit on the tray?

23. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 6) A glass has a circular base with radius 3.5 cm. A rectangular tray has dimensions 40 cm by 25 cm. How many glasses will fit on the tray? 40cm 25cm 3.5cm

24. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 6) A glass has a circular base with radius 3.5 cm. A rectangular tray has dimensions 40 cm by 25 cm. How many glasses will fit on the tray? Diameter = 2r = 2 X 3.5 = 7cm So, how many 7’s in 40? And how many 7’s in 20? 3.5cm 25cm 40cm

25. Name ______ Gr.__ Lesson 4.1 – Circles Jan.__ PRACTICE: Page 132 #’s 2,3,4,6 6) A glass has a circular base with radius 3.5 cm. A rectangular tray has dimensions 40 cm by 25 cm. How many glasses will fit on the tray? Diameter = 2r = 2 X 3.5 = 7cm So, how many 7’s in 40? And how many 7’s in 20? 5 glasses along the length & 3 glasses along the width, so 5 X 3 = 15 glasses! 3.5cm 25cm 40cm