Page 227 - SK Year 5 Mathematics DLP

MEASURING INTERIOR ANGLES

1 The size of all interior angles in a regular pentagon are equal.
What is the value of angle a ?

A protractor is used to Ways to measure the value of angle a:
measure the value of
angle a. 1 Place the centre of 2 Make sure line
the protractor at AE overlaps the
corner A. baseline of the
B C protractor.

3 Read the inner
scale from 0°
(line AE) to the
inner scale B side (line AB).
D
4 The value of a
outer scale o
is 108 or
o o o
110 − 2 = 108 .
o
108
a The value of angle a is one

A E hundred and eight degrees.
baseline centre of protractor o
108

2 State the value of angle p.
angle p corner P

P
Make sure the centre
of the protractor
p
overlaps the corner
of the angle that is
to be measured, p.

The value of angle p is .

Can you state the types of angles for a and p? Why?

• Introduce the characteristics of protractor to pupils such as the
inner scale, outer scale, baseline, and centre of protractor. 219
6.2.1 • Demonstrate how to measure angles using a protractor in detail.