Using compasses: circles and arcs

The Maths Habit

Mark a point A. Sam says there are four places exactly 4 cm from A: up, down, left and right. Is Sam right?

A

No. All the points 4 cm from A make a circle.

Compasses
A tool that draws a curve where every point is the same distance from its point.
Radius
The distance from the centre of a circle to its edge.
Locus
All the points that follow a rule.

All the points a distance from a point

  1. Set the compasses on a ruler.The point on 0, the pencil on the distance.
  2. Put the point on the centre.
  3. Turn: every point you draw is that distance away.Less than: shade inside. More than: outside.
0123452.2 cm2.2 cmA

What shape do all these points make?

3 cm from A A circle, radius 3 cm

Inside or outside the circle?

less than 2 cm from P Inside

What radius do you draw?

up to 8 m
1 cm stands for 2 m 4 cm

Draw all the points that are 2.5 cm from A. A circle, radius 2.5 cm

A2.5 cm

Draw all the points that are 2 cm from B. A circle, radius 2 cm

B2 cm

Draw all the points that are 2.5 cm from A. A circle, radius 2.5 cm

A2.5 cm

Draw all the points that are 1.5 cm from C. A circle, radius 1.5 cm

C1.5 cm

A and B are 5 cm apart. Where are the points that are 3 cm from A and 4 cm from B?

AB

Where an arc of 3 cm from A crosses an arc of 4 cm from B: two places.

Mark the points that are 3 cm from A and 4 cm from B. Two points

AB

Mark the points that are 2.5 cm from C and 3.5 cm from D. Two points

CD

Mark the points that are 3 cm from A and 4 cm from B. Two points

AB

Mark the points that are 4 cm from E and 2.5 cm from F. Two points

EF

Draw all the points that are 2.5 cm from A. A circle, radius 2.5 cm

A2.5 cm

Draw all the points that are 2.2 cm from K. A circle, radius 2.2 cm

K2.2 cm

Mark the points that are 3 cm from A and 4 cm from B. Two points

AB

Mark the points that are 2.5 cm from G and 2 cm from H. Two points

GH

Mark the points that are 3 cm from A and 4 cm from B. Two points

AB

Mark the points that are 3 cm from M and 3 cm from N. Two points

MN

Using compasses: circles and arcs worksheet, page 1

Using compasses: circles and arcs worksheet, page 2

Answer sheet

Thumbs up if it is right. Thumbs down if it is wrong.

  1. All the points 3 cm from A make a circle, radius 3 cm.

    Right

  2. The points less than 3 cm from A are on the circle.

    Wrong

  3. Two circles can cross at three points.

    Wrong

  4. If AB = 5 cm, no point is 2 cm from A and 2 cm from B.

    Right

  1. Draw a circle, radius 3 cm. Keep the compasses the same and step round it. How many steps fit?

    6

  2. A radio mast reaches 30 km. Two towns are 25 km and 35 km from it. Which gets the signal?

    The nearer one

  3. Shade the points more than 2 cm and less than 3 cm from P. What shape is it?

    A ring

  1. Draw all the points that are 1.2 cm from A.

    A circle, radius 1.2 cm
    A

  2. Mark the points that are 1.5 cm from A and 2 cm from B.

    Two points, where the arcs cross
    AB

  3. A bell is heard up to 15 m. 1 cm stands for 5 m. What radius?

    3 cm
Exit tickets to print