Quick trick for similar triangles
Similarity has suddenly become much easier to teach than when I first started my teaching career. Kids today have familiarity with the idea because of one big difference in their experiences growing up – technology. This is a super simple connection for them to make, which makes a maths concept appear simple via analogy:
Draw two triangles on the board — different sizes, but with matching angles.
Then place your hands around the smaller one and make a simple “zoom in / zoom out” gesture, like you’re resizing an image on a tablet screen.
Something clicks instantly.
Today’s students live in a world of pinch-to-zoom, drag-to-resize, and digital scaling. They intuitively understand that when you enlarge an image, every part grows in proportion and every angle stays the same. Similarity feels natural to them — far more so than it did for students of previous generations who didn’t grow up manipulating images on screens.
By linking the triangles to that familiar motion, you tap into existing intuition:
similar shapes are just resized versions of each other; same angles, scaled side lengths.
It’s a tiny gesture, but it meets students where they already are, making similarity feel obvious instead of abstract. And it really pays dividends later when they can understand trigonometry in terms of similar triangles.
