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7th grade · Math · Unit 5 of 15

Circles

Circumference, area and π

What your child practices

Using radius, diameter and π (about 3.14) to find the distance around a circle and the area inside it, including real objects like wheels and pizzas.

Minnesota K-12 Academic Standards benchmark: 7.2.3.1; 7.2.3.2 · the circumference and area of circles

How we explain it

Children can open this short lesson before they practice.

  1. The radius goes from the center to the edge. The diameter goes all the way across: d = 2r.
  2. Circumference (the distance around) is C = π × d.
  3. Area is A = π × r × r. Use π ≈ 3.14.

Example: A circle has diameter 10 cm. What is its circumference? C = π × d. C ≈ 3.14 × 10 = 31.4. Answer: About 31.4 cm

Circles in Minnesota

In the Minnesota K-12 Academic Standards, this is unit 5 of 15 in 7th grade Math, after Two-Step Equations and before Probability.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Minnesota Department of Education (MDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    A circle has a radius of 3 cm. What is its area? Use 3.14 for π and round to one decimal place.

    ⭕r = 3 cm

    answer boxcm²

  2. Question 2

    A circle's circumference is 106.76 cm. What is its diameter? (Use 3.14 for π.)

    answer boxcm

  3. Question 3

    What is the diameter of a circle?

    • The distance from the center to the edge
    • The space inside the circle
    • The distance around the circle
    • The distance across the circle through its center

  4. Question 4

    A circle has a diameter of 45 cm. What is its circumference? Use 3.14 for π and round to one decimal place.

    ⭕d = 45 cm

    answer boxcm

  5. Question 5

    A circle has a radius of 24 m. What is its circumference? Use 3.14 for π and round to one decimal place.

    ⭕r = 24 m

    answer boxm

  6. Question 6

    A circle has a radius of 29 cm. What is its diameter?

    ⭕r = 29 cm
    • 29 cm
    • 14.5 cm
    • 116 cm
    • 58 cm

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