Grade 3Math
How to Use a CompassDraw circles, copy lengths, and draw patterns
A compass is a tool for drawing circles and copying lengths. Let's look, step by step, at how to hold it, open it, and turn it.
The narration and the pictures are in Japanese. You can hear the same words that are used in class at a Japanese school.
- Video
- 1:50（9 scenes）
- Problems
- 2 problems
Open this lesson in Japanese（コンパスの 使い方）
Let's try
Write the math sentence in your notebook first, then open the answer.
-
1To draw a circle with a radius of 4 cm, how wide do you open the compass, from the needle to the tip of the pencil: 8cm, 2cm, or 4cm?
Hint
The needle goes at the center, and the pencil touches the edge. What do we call the line from the center to the edge?
Answer
It is 4cm. You open a compass to the length of the radius. It is not the diameter, 8 cm.
-
2What happens if the opening of the compass changes while you are drawing a circle?
Hint
The radius should be the same length everywhere.
Answer
The circle may not join up, or it may become a double line. Keep the opening the same and turn it slowly.
Words in this lesson
- compass コンパス
- A tool for drawing circles and copying lengths.
- radius 半径
- A straight line drawn from the center of a circle to the edge of the circle. Its length is also called the radius.
- center 中心
- The point in the middle of a circle.
For parents and guardians
- The names of lessons and the order of topics differ slightly between textbooks. This page follows the content of Japan's national curriculum guidelines (the Course of Study).
- The needle of a compass is sharp, so please have your child use it on a desk and never point it at anyone. When turning it, holding only the knob (the part you hold) makes the opening less likely to change.
- If your child can't draw neatly, check whether the screw has loosened and the opening has changed, and whether the needle tip has slipped off the center point. If the needle tip slides, please put a compass mat or something similar underneath.