Area of a circle, and of parts of a circle

Answer Key - Grade 7 Math Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. Read this first

   Use this

   Grid, each square 0.5 cm by 0.5 cm. The wedges laid point up, point down make a near-rectangle 7.85 cm wide (half the distance around the circle) and 2.5 cm tall (the radius).

2. 1.

   Ari cuts a round cookie into equal wedges and lays them point up, point down into a near-rectangle. The wedges are very well behaved. What is the area of the cookie in square cm?

   19.625
3. 2.

   Bo cuts a round pizza into equal wedges and lays them point up, point down into a near-rectangle. The slices lined up like a team. What is the area of the pizza in square cm?

   200.96

4. Use this

   Grid, each square 1 cm by 1 cm. A circle with its diameter 9 cm drawn across and its radius 4.5 cm drawn from the middle to the edge. Below it, the wedges laid out as a rectangle 4.5 cm tall and 3.14 radii wide.

5. 3.

   Milo's hand mirror is 9 cm across, so its radius is 4.5 cm. It checks for smudges. What is its area in square cm?

   63.585
6. 4.

   Pia's dish is 25 cm across, so its radius is 12.5 cm. It has big dreams. What is its area in square cm?

   490.625

7. Use this

   Grid, each square 1.3 cm by 1.3 cm. A circle with its diameter 13 cm drawn across and its radius 6.5 cm drawn from the middle to the edge. Below it, the wedges laid out as a rectangle 6.5 cm tall and 3.14 radii wide.

8. 5.

   Ren's plate is 13 cm across, so its radius is 6.5 cm. It has a big attitude. What is its area in square cm?

   132.665

9. Use this

   Grid, each square 1 cm by 1 cm. A circle with its radius 5.5 cm drawn from the middle to the edge; the distance around it is 34.54 cm. Below it, the wedges laid out as a rectangle one radius tall and half the circumference wide.

10. 6.

    Tala's hand mirror has a radius of 5.5 cm and a circumference of 34.54 cm. It likes what it sees. What is its area in square cm?

    94.985
11. 7.

    Zee's plate has a radius of 10 cm and a circumference of 62.8 cm. It would like to be a frisbee. What is its area in square cm?

    314

12. Use this

    Grid, each square 1 cm by 1 cm. A circle with its radius 6 cm drawn from the middle to the edge; the distance around it is 37.68 cm. Below it, the wedges laid out as a rectangle one radius tall and half the circumference wide.

13. 8.

    Ari's clock face has a radius of 6 cm and a circumference of 37.68 cm. Tick, tick, tidy. What is its area in square cm?

    113.04

14. Use this

    Grid, each square 4 cm by 4 cm. A circle with its radius 16 cm drawn from the middle to the edge; the distance around it is 100.48 cm. Below it, the wedges laid out as a rectangle one radius tall and half the circumference wide.

15. 9.

    Bo's pizza has a radius of 16 cm and a circumference of 100.48 cm. It has a lot of wedges. What is its area in square cm?

    803.84
16. 10.

    Esme's pizza has a radius of 17.5 cm and a circumference of 109.9 cm. It is a very large pizza. What is its area in square cm?

    961.625