Parts of a circle: radius, diameter, circumference and area
Grade 7 Math Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
A round pond is 62.8 m around. Ari wants its area, the space inside the edge. Use 3.14 for π. What is the area in square meters?
A round garden bed is 31.4 m around. How many square meters of soil does Bo need to cover it? Use 3.14 for π.
A round rug is 94.2 cm around. What is its area in square centimeters, Esme? Use 3.14 for π.
A track has two straights of 85 m and two curved ends that together make a circle 30 m across. Kira runs 3 laps. How far? Use 3.14 for π.
A track has two straights of 75 m and two curved ends that together make a circle 40 m across. Luz runs 4 laps. How far? Use 3.14 for π.
A track has two straights of 100 m and two curved ends that together make a circle 50 m across. Noah runs 5 laps. How far? Use 3.14 for π.
One round pond has a radius of 3 m. Another has a radius of 6 m. How do the second pond's distance around and area compare with the first's, Pia?
- Both are 2 times as much, because the radius is 2 times as big.
- Both are 4 times as much, because 6 × 6 is 4 times as big as 3 × 3.
- Its distance around is 4 times as long and its area is 2 times as big.
- Its distance around is 2 times as long and its area is 4 times as big.
A 12-inch pizza (across) and a 6-inch pizza (across) have the same thickness of dough. How much more dough does the 12-inch pizza need, Ren?
- 6 times as much, because 12 − 6 = 6 more inches across the pizza.
- 3.14 times as much, because circle comparisons use the number π.
- 4 times as much, because its area is 2 × 2 = 4 times as big.
- 2 times as much, because the distance across is 2 times as big.
Tala cuts a circle into thin wedges and lays them point up, point down into a near-rectangle. Its width is half the circumference and its height is the radius. Which area rule follows?
- Area = ½ × circumference × diameter = ½ × 2πr × 2r = 2πr²
- Area = circumference + radius = 2πr + r
- Area = circumference × radius = 2πr × r = 2πr²
- Area = ½ × circumference × radius = ½ × 2πr × r = πr²
Three students measure round lids, distance around and across: Ari 31.4 cm and 10 cm, Ren 50 cm and 25 cm, Luz 94.2 cm and 30 cm. Whose measurements are probably off, Zee?
- No pair, because lids have different sizes, so their ratios do not need to match.
- Ari's, because 31.4 is not a whole number, and measurements should be whole.
- Ren's, because 50 ÷ 25 = 2, far from the 3.14 that the other two lids give.
- Luz's, because 94.2 cm is the biggest distance around, so it is likely to be wrong.
