The circle is an important shape in geometry, with many important terms and relationships to understand. This activity will help your child grasp the concepts of circumference, radius and diameter and better conceptualize how they fit together.
What You Need:
- Pen
- Paper
- String
- Ruler
What You Do:
- Ask your child to measure the piece of string with the ruler and write down the length.
- Help your child make a circle using the piece of string, placing it on a table. Review the term “circumference,” which is the distance around the edge of the circle. Explain that the length of the string is equal to the circumference, because if you were to undo the circle you would have the same length of string and the string is what comprises the distance around the circle. Try to make sure she understands that the length of string and the circumference are equal.
- Next, review the term “diameter”. The diameter is the distance from one edge of the circle to the other that goes through the center of the circle. To show what the diameter looks like, get a second piece of string and place it in the middle of the circle from one edge to the other, cutting off any extra string that extends past the circle’s border. This straight piece of string going through the center of the circle is the diameter.
- Take the diameter string off of the circle. Take a third piece of string and cut it so that it is half the length of the piece of string representing the diameter. Place this piece of string from the center of the circle to one of the edges of the circle and explain that this piece of string represents the radius. Reiterate the fact that the radius is one half the length of the diameter.
- Once your child sees the relationships between these terms, do a practice problem using the pieces of string. Remind your child that the equation for circumference is 2πr, which is 2 times pi times the radius. Take the measurement of the first piece of string and use it to calculate what the radius should be. Another very useful concept in geometry to explain to your child is that if you know one of the relationships of the circle, either diameter, radius, or circumference, you can calculate all of the other values. So when doing math problems, she should focus on finding one of those values in order to be able to find the other values.
Related learning resources
Pumpkin Measurements
Activity
Pumpkin Measurements
This fun activity encourages your child to develop their skills in not only taking measurements, but also in working with the measurements themselves.
4th grade
Math
Activity
Estimating Measurements
Worksheet
Estimating Measurements
Help your child practice "eyeballing" these measurements in inches and centimeters.
2nd grade
Math
Worksheet
Circle Parts
Worksheet
Circle Parts
Help ingrain circle vocabulary in your fifth grader's mind with this second worksheet based on naming a circle's components.
5th grade
Worksheet
Tree Measurements
Worksheet
Tree Measurements
Bust out the measuring tape, it's time to make some tree measurements! Use the mini ruler to help you measure how tall each tree is.
preschool
Math
Worksheet
Graduated Cylinder Measurements
Worksheet
Graduated Cylinder Measurements
Give your budding scientist some practice, by reading measurements on graduated cylinder illustrations.
4th grade
Math
Worksheet
Circle Shapes
Worksheet
Circle Shapes
Help your child learn circle shapes by looking for them around the house. Find 5 everyday things shaped like circles and draw them in the spaces.
1st grade
Math
Worksheet
Circle Graph
Worksheet
Circle Graph
Your little baker will practice analyzing the data in a circle graph (or pie chart).
2nd grade
Math
Worksheet
Reading Liquid Measurements
Worksheet
Reading Liquid Measurements
Boost your third grader's math skills with this colorful worksheet that gets him to practice reading liquid measurements.
3rd grade
Math
Worksheet
Circumference and Area of a Circle
Worksheet
Circumference and Area of a Circle
With this pizza circle sheet, your student will practice finding the radius, diameter, circumference and area of a circle.
Worksheet
Circle the Adverbs, Quickly!
Worksheet
Circle the Adverbs, Quickly!
In this playful grammar worksheet, learners will find and circle the adverb in 10 sentences.
2nd grade
Reading & Writing
Worksheet
Converting Metric Measurements to Decimals & Fractions
Lesson plan
Converting Metric Measurements to Decimals & Fractions
Marry metric measurements to the everyday world around you! Use this lesson plan to teach your class the fun of converting metric measurements into fractions.
4th grade
Math
Lesson plan
Circle Ten and Solve
Worksheet
Circle Ten and Solve
Use this nifty worksheet to learn about the "circle ten" shortcut.
2nd grade
Math
Worksheet