Solids, angles and quadrilaterals · Usually met around P2
Right, acute and obtuse angles
Smaller than a right angle: acute; bigger: obtuse.
How to do it
Method
Smaller than a right angle: acute; bigger: obtuse
Minute hand on 12, hour hand on 2: 2 steps < 3, acute
Another way
Set square
Other side outside the square: obtuse
In full
A right angle is like the corner of a book or a sheet of paper; so do a clock's hands with the minute hand on 12 and the hour hand on 3. Check with a set square (or paper folded twice into a right angle): line up the vertex and one side; if the other side lies along it, it's a right angle; inside it, smaller, it's acute; outside it, bigger but not yet a straight line, it's obtuse. Or think of a clock: hands 3 big steps apart make a right angle, fewer is acute, 4 or 5 is obtuse, and 6 is a straight line.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
What kind of angle is this?
- A. Right angle
- B. Not an angle
- C. Obtuse
- D. Acute
Choose the right answer
Show the answer and working
Answer: A. Right angle
Check with a set square: matching is a right angle, smaller is acute, bigger is obtuse.
Example 2
How many right angles does this shape have?
Show the answer and working
Answer: 4 right angles
Check each corner with a set square: 4 right angles.
Example 3
This angle is acute.
True or false?
Show the answer and working
Answer: True
An acute angle is smaller than a right angle: check with a set square.
Practise it in the game →Solids, angles and quadrilaterals · Free to start, unlimited questions, no download