The idea in brief. Check each requested opening and count it once. A point can belong to more than one opening. Mark each requested opening once. Check a corner against a right angle before calling it one. In the lesson. In the previous lesson, you compared an angle with the corner of a square. Today, we will find the marked angles in a figure and count the ones the question asks for. Check each marked angle and count it only once. Two or more angles can share the same point.
Lesson video, with the working
Count angles
4 min 42 s
The film teaches 3 questions in turn. Each question shows first; its working is written as the film explains it.
Mei draws a straight line across a rectangular card. She marks angles a to g. How many of the marked angles are smaller than a right angle?
Angles smaller than a right angle: a, b, c.
Number of angles = 3
Ans: 3
Example 1 of 2
Mei cuts a card into this shape. She marks angles h, j, k, m, n and p inside it. How many of the marked angles are right angles?
Right angles: h, j, m, n, p.
Number of right angles = 5
Ans: 5
Example 2 of 2
Mei draws three straight lines that cross at one point. She marks angles r, s, t, u, v and w. How many of the marked angles are smaller than a right angle?
Angles smaller than a right angle: r, s, u, v.
Number of angles = 4
Ans: 4
How to solve it
Read what the question asks you to count: angles smaller than a right angle, or right angles.
Check each marked angle against the corner of a square.
If it fits inside the corner, it is smaller. If it fits exactly, it is a right angle. If it is wider, it is greater.
Count only the angles the question asks for, and count each one once.
Two or more angles can share the same point, so check every marked angle.
Check each angle on the side where its mark is drawn, and fit the corner of the square there.
Check each marked angle and count it only once. Two or more angles can share the same point.
Practice questions with worked solutions
Question 1 is free to try. The other 6 open in the free trial, each with its solution film.
Each of the four inside corners matches a corner of a square.
Number of right angles = 4
Ans: 4 right angles
Answer: 4 right angles
For parents
How should a P3 child go about counting angles in a figure?
Once your child can compare one angle with a right angle, this Primary 3 subtopic asks them to do it many times in one figure, sorting the marked angles and counting the ones a question asks for.
What your child learns here
Once your child can compare one angle with a right angle, this Primary 3 subtopic asks them to do it many times in one figure, sorting the marked angles and counting the ones a question asks for.
Find each marked angle, with its two arms and the point where they meet.
Compare each one with a right angle: smaller, equal or greater.
Count only the angles of the kind the question asks for, each one once.
Several angles can share one meeting point, and each still counts as its own angle.
Does the answer make sense?
When the question asks how many, the answer cannot be more than the number of corners and marked openings in the figure. A rectangle or square always gives exactly four right angles inside it, which is a handy anchor when your child counts the larger or combined figures.
How to practise these questions
The Basic questions practise finding the angles inside a simple shape. The Intermediate questions add counting angles of a certain kind in shapes with more sides, including ones larger or smaller than a right angle. When counting angles is stuck, play that question's solution film and return to it later from Revision. Its multiple-choice Basic questions show two rows of marked angles and ask how many are smaller, or how many are greater, than a right angle; their solutions are written out step by step, with no film.
Questions parents ask
Why are angles marked with letters? The letters let a child point to one opening at a time, even when several openings share one corner. They also let the answer show exactly which angles were counted.
Is a straight line an angle in P3? At this level a straight line is not counted as one of the angles to compare. It is a half turn, which is two right angles together, so it is never a right angle.
Can a triangle have a right angle? Yes, some triangles have one right angle, but many have none. Each corner has to be checked with a square corner rather than assumed.
