Identify right angles; recognise that two right angles make a half-turn, three make three-quarters, and four make a complete turn
A right angle is a square corner. It is the corner you see on a square, a rectangle, or the corner of this page. A rectangle has four corners, and every one of them is a right angle. Turning a shape does not change its corners. Longer or shorter arms do not change an opening.
Zara stands at the centre of a big clock on a flat floor. She faces the 12, then turns clockwise to face the 3. That turn is a quarter turn, and it makes exactly one right angle.
One right angle is a quarter turn. Two right angles make a half turn. Three right angles make three-quarters of a turn. Four right angles bring you all the way around: a full turn. The right angle amount is the same wherever you start on the clock.
The easiest right-angle checker is the corner of a rectangular sheet. Put the sheet's corner point on the corner you are testing. Align one edge with one side of the corner. Look at the other edge. If it matches exactly, the corner is a right angle. If the corner is narrower, it is less than a right angle. If it opens wider, it is more than a right angle.
A right angle is a good corner to test other corners against. If the checker fits with no gap, the corner is a right angle. If the corner is narrower, it is less. If it opens wider, it is more.
A right angle is a square corner, and four right angles make one full turn all the way around.
Extra items and three readings are authored originals. One reading is adapted from Khan Academy 'Right angles in shapes (informal definition)'. Two videos are Khan Academy 'Recognizing angles' and 'Acute, right, & obtuse angles'.
You already know an angle can be a corner or a turn, like a door swinging open. Zara stands at the centre of a big clock with numbers marked on the floor. She faces the 12, then she turns clockwise to face the 3.
What is Zara's turn called?
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