RIC-20153 ACM Measurement and Geometry (Yr 3) Geometric reasoning

Sub-strand: Geometric reasoning—GR – 1
HANDS–ON ACTIVITIES
• In this unit, students will mostly compare angles to the right angle (90°). This would involve recognising that a straight
angle is two right angles (180°) and a full turn is four right angles (360°). Discuss the idea that right angles occur all
around us, including the corners of pieces of paper, books, corners in rooms etc.
• One method of introducing
students to the idea of angles is
to get them to (very carefully)
trace the cutting edge of an
open pair of scissors.
• Students make an angle demonstrator (see page 77). They use these to show various angles such as 90°, an angle
less than 90°, an angle greater than 90°, a straight angle and a full turn. Students find ways to record their results. Play
games where the teacher (or a student) calls out an angle size (from the five mentioned above) and the students make
that angle with their angle demonstrator and hold it up for the teacher to check.
• Students make an angle unit measure that can be
used as a non-standard unit. One version of this is to
cut a sharp angle from a piece of cardboard. Allow the
students to decide on how ‘pointy’ the angle is, but
‘quite pointy’ would be the instruction. Students then
use their angle unit measures to measure different
angles. Note that as the students have each decided
on the ‘pointiness’ of their angle unit measure, there
will be a variation of results for the same measuring
activity, as there is when measuring the length of a
table using the non-standard unit of hand spans.
• Another way to compare angles without a
protractor is for students to make a different type
of angle unit measure. This involves using a circle
of light card. Students fold the circle in half, in half
again, a third time, and finally a fourth time. When
this is opened out, there are 16 equal (or very nearly
equal) segments that become the units of the
angle unit measure. Students then can use these to
measure the size of angles in terms of the number
of segments needed on their angle unit measure.
Students may make the link to the fact that four of
these angle unit segments make a right angle (90°).
My angle demonstrator is showing a straight line, which is 180°.
My angle unit
measure
©R.I.C. Publications
Low Resolution Images
Display Copy
I needed 4 of my angle unit segments to be
the same as the corner of my book.
74 Australian Curriculum Mathematics resource book: Measurement and Geometry (Year 3) R.I.C. Publications ® www.ricpublications.com.au