MathGrade 4ages 9–10
📐 Right angle
A right angle has a precise meaning — a quarter turn, 90 degrees — but to a child, any corner that looks reasonably sharp can seem "square enough" without actually checking it.
Try this lesson freeNo card needed. The first lesson is free.
Download on the App StoreWhat your child learns
- A whole turn is 360 degrees.
- A quarter of the turn is 90, and that is a right angle.
- The corner of a rectangular page is exactly that.
- Less than 90 is acute, more than 90 is obtuse.
The mistake most kids make here
Any sharp corner looks like a right angle.
Try one question
The corner of a rectangular page. Which angle is it?
The corner
- acute
- right
- obtuse
Answer
right — Yes. All four corners of the page are a quarter turn.
How Maya teaches it
Your child tells Maya what they did in class. She teaches this topic at her desk, asks questions with tappable answers, and when the answer is wrong she explains why that answer was tempting instead of saying “try again”. She remembers what did not land and comes back to it.
Your child has it when they can: Say how to check a right angle without a tool.
How to help at home
Children often judge angles by eye, and a sharp-looking corner and a true right angle can look similar at a glance. The fix is giving them a fixed, reliable way to check, rather than relying on how a corner "looks".
Tear a piece of paper and fold it in half, then in half again — the folded corner is a guaranteed right angle. Use that folded corner to test other corners around the house: a book, a window, a picture frame, a slice of toast.
When your child says a corner "looks right-angled" without checking, say: "let's test it with our folded paper corner" and hold the fold up against the corner in question to see if it matches exactly.
A sign they've got it: they reach for the folded-paper test (or another fixed right angle) before answering, instead of deciding just by looking at the corner.
Questions parents ask
- Why does my child think every sharp corner is a right angle?
- Without a reliable way to check, children judge angles by how pointy or sharp they look, and a sharp angle can be mistaken for a right one. A folded-paper corner gives them a physical, repeatable test.
- What age do children learn about right angles?
- Right angles are typically introduced around grade 4, alongside the broader idea of measuring angles in degrees.
- How do I explain acute and obtuse angles at the same time?
- Once the folded-paper right angle is established as the reference, acute (narrower, more pointed) and obtuse (wider, more open) angles are easy to compare against it — narrower than the fold is acute, wider is obtuse.
- How does Maya teach right angles?
- Maya asks the child to compare a shown angle against a known right angle before naming it, so the answer comes from a check rather than a guess by eye.
No card needed. The first lesson is free.
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