Quadrilaterals: common misconceptions

If your child says… “A corner pointing inward rules it out.”

Ask together

Where does this boundary gain an extra side or lose its closure?

What’s true

An inward corner is allowed when four straight edges close without crossing.

If your child says… “We must still measure the sides before naming it.”

Ask together

Can opposite edges move closer together while both stay perpendicular to the same edge?

What’s true

Four right corners already guarantee the opposite sides match.

If your child says… “The folds meet at 45°, and each corner half is 90°.”

Ask together

Which fold halves an original right corner?

What’s true

A corner half measures 45°, while the central crossing measures 90°.

If your child says… “The last corner can have any angle.”

Ask together

After the other corners use their share, how much of 360° remains?

What’s true

Fixing three angles leaves only one possible fourth angle.

If your child says… “Halving the diagonals means they cross at 90°.”

Ask together

Do the matching ticks describe lengths or the angle where the diagonals cross?

What’s true

Each diagonal has two equal halves. The diagonals can differ in length and cross without right angles.

If your child says… “Diagonals crossing at 90° must have equal lengths.”

Ask together

Does the shorter fold reach as far as the longer fold?

What’s true

A rhombus can have perpendicular diagonals of different lengths.

If your child says… “A second parallel pair stops it being a trapezium.”

Ask together

Does having two pairs include having at least one?

What’s true

Here, having extra parallel sides still meets the trapezium condition.

If your child says… “Kites and parallelograms cannot belong together.”

Ask together

Which arrows show that rhombuses belong to both families?

What’s true

Rhombuses satisfy both families because their equal sides meet and their opposite sides run parallel.