Circle Diameter Practice Problems - Step-by-Step Solutions

Master diameter calculations with interactive practice problems. Learn to find diameter from radius, circumference, and area with detailed solutions and explanations.

📚What You'll Master in This Practice Session
  • Calculate diameter when given the radius using the formula D = 2r
  • Find diameter from circumference using the relationship P = πD
  • Determine diameter from circle area using A = πr² and conversion steps
  • Solve real-world problems involving pizza slices, circular areas, and geometric shapes
  • Apply diameter concepts to complex geometry problems with trapezoids and triangles
  • Work with sector areas and central angles in diameter-related calculations

Understanding Diameter

Complete explanation with examples

A diameter is a section that connects two points that lie on the circumference, that passes through the center of the circle. The diameter is actually twice the radius.

As in the case of the radius, as well as in the case of the diameter, there are an infinite number of diameters on the circumference, and all are identical in length.

Below is an example of a circle with several diameters marked in different colors.

Diameter

Detailed explanation

Practice Diameter

Test your knowledge with 11 quizzes

True or false:

The radius of a circle is the chord.

Examples with solutions for Diameter

Step-by-step solutions included
Exercise #1

All ____ about the circle located in the distance ____ from the ____ circle

Step-by-Step Solution

To solve this problem, we will consider the parts of a circle and how they interplay based on the description provided in the incomplete sentence:

  • Step 1: Recognize that the first blank needs a term that refers to the primary element defining a circle externally.
  • Step 2: The second blank needs a term associated with 'equal' as it describes distances from a specific location, hinting at a property of circles.
  • Step 3: The third blank likely wants us to relate this location to the circle itself, denoting the standard geometric reference point.

Now, let's fill in each blank systematically:

The first term 'Point' refers to all points lying on the perimeter of a circle. In the definition of a circle, each point on the circle’s circumference maintains an equal distance from its center.

The second term 'equal' pertains to how all these points are at an equal distance - which is the radius - from the center.

The third term 'center' specifies the reference point within the circle from which every point on the circle is equidistant.

Thus, the complete statement is: "All point about the circle located in the distance equal from the center circle."

The correct choice that completes the sentence is: Point, equal, center.

Answer:

Point, equal, center

Exercise #2

If the radius of a circle is 5 cm, then the length of the diameter is 10 cm.

Step-by-Step Solution

To determine if the statement "If the radius of a circle is 5 cm, then the length of the diameter is 10 cm" is true, we need to use the relationship between the radius and diameter of a circle.

The diameter d d of a circle is calculated using the formula:

d=2r d = 2r

where r r is the radius. In this problem, the radius r r is given as 5 cm.

Using the formula, the diameter is:

d=2×5cm=10cm d = 2 \times 5 \, \text{cm} = 10 \, \text{cm}

This matches exactly the length of the diameter given in the problem.

Therefore, the statement "If the radius of a circle is 5 cm, then the length of the diameter is 10 cm" is True.

Answer:

True

Exercise #3

M is the center of the circle.

Perhaps AB=CD AB=CD

MMMAAABBBCCCDDDEEEFFFGGGHHH

Step-by-Step Solution

CD is a diameter, since it passes through the center of the circle, meaning it is the longest segment in the circle.

AB does not pass through the center of the circle and is not a diameter, therefore it is necessarily shorter.

Therefore:

ABCD AB\ne CD

Answer:

No

Video Solution
Exercise #4

The number Pi (π) (\pi) represents the relationship between which parts of the circle?

Step-by-Step Solution

To solve this problem, we will clarify the relationship between the constant π\pi and parts of a circle.

The number π\pi is a constant that relates the circumference of a circle (the perimeter) to its diameter. The formula for the circumference CC of a circle is given by:

C=π×d C = \pi \times d

where CC is the circumference, and dd is the diameter of the circle. This equation shows that π\pi is the ratio of the circumference of a circle to its diameter, which remains constant for all circles.

Therefore, π\pi indeed represents the relationship between the circle’s perimeter and its diameter.

Thus, the correct answer is: Perimeter and diameter

Answer:

Perimeter and diameter

Exercise #5

There are only 4 radii in a circle.

Step-by-Step Solution

A radius is a straight line that connects the center of the circle with a point on the circle itself.

Therefore, the answer is incorrect, as there are infinite radii.

Answer:

False

Frequently Asked Questions

What is the diameter of a circle and how is it different from radius?

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The diameter is a straight line that passes through the center of a circle, connecting two points on the circumference. It is exactly twice the length of the radius (D = 2r). While radius measures from center to edge, diameter measures across the entire circle through its center.

How do you find the diameter if you know the circumference?

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Use the formula D = P/π where P is the circumference. Since circumference equals π × diameter, you simply divide the circumference by π (approximately 3.14) to get the diameter.

What formula do you use to calculate diameter from area?

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First find the radius using r = √(A/π), then multiply by 2 to get diameter: D = 2√(A/π). This works because area equals πr², so you solve for r first, then convert to diameter.

Can a circle have multiple diameters?

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Yes, a circle has infinite possible diameters, but they are all equal in length. Every diameter passes through the center and has the same measurement, regardless of its orientation or position.

How do you solve diameter problems involving sectors and central angles?

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For sector problems, use the relationship that sector area = (θ/360°) × πr² where θ is the central angle in degrees. Find the radius first, then calculate diameter as D = 2r. The sector angle helps determine what fraction of the total circle area you're working with.

What are common mistakes when calculating circle diameter?

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Common errors include: 1) Confusing radius and diameter (forgetting to multiply/divide by 2), 2) Using incorrect π value in calculations, 3) Forgetting to square the radius in area formulas, 4) Not converting units properly in word problems.

How is diameter used in real-world applications?

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Diameter calculations appear in many practical situations: determining pizza slice areas, calculating material needed for circular objects, measuring wheel sizes, designing circular gardens or pools, and engineering applications involving pipes, gears, and circular components.

What is the relationship between diameter and other circle measurements?

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Key relationships include: Diameter = 2 × radius, Circumference = π × diameter, Area = π × (diameter/2)². These formulas allow conversion between any circle measurements when you know just one value.

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