Grade 7- Circles

Circle information

100

What would you use from your protractor kit to make a circle?

Compass

200

What is (distance around) divided by (diameter)? 

Pi

300

What is (distance around) divided by (radius)? 

2pi

400

What are the equations for finding the radius and diameter?

radius= d ÷ 2 diameter =r x 2

500

What is the radius of a circle with a diameter of 95m? (leave your answer in cm)

4750 cm

Circumference

100

What does circumference mean?

the distance around a circle (like perimeter of square)

200

What is the equation for circumference? (both equations)

c=pi x d or c= pi x 2 x r

300

What is the circumference of a circle if it has a diameter of 5.2 m?

answer: 16.33 m c=3.14 x 5.2 c= 16.33 m

400

If you are given a radius of 6cm, what is the circumference?

12π cm

500

What is the diameter of a circle that has a circumference of 221mm? (round to nearest hundredth)

c= π x d 221mm = 3.14 x d 221/3.14 =d d=70.38mm

Area

100

What is the equation for the area of a circle?

A = pi x r x r

200

If you have a circular mirror with a radius of 20cm, what is its area?

A= π x 20x 20cm A = 400π cm²

300

A circle has a diameter of 25cm. What is it's area?(2 decimal places)

r=12.5cm 

A=π x 12.5 x 12.5 

= 490.63cm²

400

The area of a circle is about how many times the square of its radius? a.1 b.2 c.3 d.4

answer: 3

500

Fourty-four metres of fencing is used to make a circular enclosure. What is the area of the circle? (to the nearest square metre)

44 is the circumference 

44=3.14 x d 14.01= d r=7.01 A= π x r x r A= 3.14 x 7.01 x 7.01 A=154 m²

Circle graphs

100

How much should all the percents in a circle graph add up to?

100%

200

If a class has 28 students and 40% of them have blonde hair, how many students have blonde hair (round to the nearest whole number?

11 or 12 students have blonde hair

300

Which information should not be in a circle graph? 1) white- 78%, pink 33%, brown 28%, red 42% 2) white 24%, pink 33%, brown 33%, red 29% 3) white 20%, pink 28%, brown 44%, red 8%

number 1 and 2 should not be in a circle graph. Number three can be a circle graph.

400

There are 22 bouncy balls 8 are blue, 10 are red, and 4 are yellow. What is the percent of the BLUE bouncy balls? What would the value of its CENTRAL ANGLE be in a circle graph?

8/22 = .36 which is 36 %. central angle = .36 x 360 = 129.6 degrees

500

Show the information on internet use from a grade 7 class. There are 30 students in the class. 3 people use the internet once a week, 9 people use the internet 3 times a week, 18 people use the internet every day. (you will need to find the % of the total and the central angle in order to complete this question.)

3- 10%, 36 degrees. 9- 30%, 108 degrees. 18- 60% 216 degrees

Others

100

what is the area of a circle with a 2.4 cm radius? (to the nearest tenth)

A=3.14x 2.4 x2.4 A=18.1cm^2

200

true or false: If the radius of a circle is doubled, then the circumference is also doubled?

Always true

300

When drawing a circle graph, what tools should you use: 1) to measure each section? 2) to draw the circle? 3) to find the radius or diameter?

1) to measure the sections you use a protractor 2) to draw the circle you need a compass 3) to find the radius or diameter you need a ruler

400

The measure of space covered by a 2-D shape is the definition for what? And Find this if you have a radius of 5cm.

area =78.5 cm^2

500

The outer ring of the Canadian toonie has an outside diameter of 28mm and an inside diameter of 8mm. What is the area of the outer ring to the nearest hundredth of a square millimeter?

414.48mm^2