Parts of a circle: radius, diameter, circumference and area

Answer Key - Grade 7 Math Worksheet - Building Confidence

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

1. 1.

   Ari's bike wheel has a radius of 35 cm. About how far does the bike roll in one full turn of the wheel? Use 3.14 for π.

   219.8 cm
2. 2.

   A round pond has a radius of 12 m. How far does Bo walk once around its edge? Use 3.14 for π.

   75.36 m
3. 3.

   A Ferris wheel has a radius of 45 ft. How far does a seat travel in one full turn, Esme? Use 3.14 for π.

   282.6 ft
4. 4.

   A drum is 50.24 cm around. Kira wants to know how far across (the diameter) it is. Use 3.14 for π.

   16 cm
5. 5.

   Luz's round plate is 87.92 cm around. How many cm across (the diameter) is the plate? Use 3.14 for π.

   28 cm
6. 6.

   A tree trunk is 113.04 cm around. Milo wants its diameter, the distance straight across. Use 3.14 for π.

   36 cm
7. 7.

   Noah measures a round bowl and finds it is 69.08 cm around. How many cm across is the bowl? Use 3.14 for π.

   22 cm
8. 8.

   Pia measures three round things, distance around and across: a can (31.4 cm, 10 cm), a bucket (62.8 cm, 20 cm), a drum (94.2 cm, 30 cm). What does around ÷ across give?

   • A bigger number for bigger circles, because a bigger circle has more distance around.
   • About 2 each time, because the distance around is twice the distance across.
   • About 6.28 each time, because the distance around is two times 3.14 across.
   • About 3.14 each time, however big the circle is.
9. 9.

   Ren wants a quick estimate, without a calculator, of the distance around a round trampoline that is 4 m across. Which estimate is the most reasonable?

   • About 8 m, because the distance around is twice the 4 m across.
   • About 6 m, because the distance around is 3 times half the 4 m across.
   • About 12 m, a little more than 3 times the 4 m across.
   • About 16 m, because the distance around is 4 times the 4 m across.
10. 10.

    Tala's round rug is 2 m across. Edge fringe is sold by the meter and top cleaner by the square meter. Which pair of amounts is right? Use 3.14 for π.

    • Fringe: 6.28 m (circumference). Cleaner: 3.14 square m (area).
    • Fringe: 3.14 m (area). Cleaner: 6.28 square m (circumference).
    • Fringe: 12.56 m (circumference). Cleaner: 3.14 square m (area).
    • Fringe: 6.28 m (circumference). Cleaner: 12.56 square m (area).