Shapes that fit over each other exactly
Geometric twins
Cut two triangles from one template, lay one on the other, and it disappears underneath.
Shared by a Veda teacher · Generated with Veda AI · Oct 2026
Veda Bites are swipeable micro-lessons — each one teaches exactly one idea. Here's a taste from this kit; the app has the full deck.
Geometric twins
Cut two triangles from one template, lay one on the other, and it disappears underneath.
The test is covering
Two shapes seen side by side can easily mislead the eye.
Turning and flipping are allowed
The second shape may need turning, or even flipping over, before it fits.
You need not check all six
Two triangles have six measurements each, three sides and three angles.
Three sides are enough
Give the three sides as 5 cm, 6 cm and 9 cm, and only one triangle fits.
Why three sides settle it
Draw the longest side, then sweep an arc from each end with the other two lengths.
Congruent shapes fit over each other exactly, after any turning or flipping needed. The same shape alone is not enough, and the same size alone is not enough either. A congruence statement carries a correspondence in the…
~35 min · full explanation, examples & memory tricks in the app
Three well-chosen measurements prove congruence, and four criteria do the work: SSS, SAS, ASA and RHS. Each names at least one side, because angles alone fix only the shape. Three angles leave the size open, and two side…
~45 min · full explanation, examples & memory tricks in the app
Folding an isosceles triangle makes two halves congruent by SSS, which proves the base angles equal. From the apex the base angles follow, and from a base angle the apex follows. Every equilateral triangle has 60 degree…
~40 min · full explanation, examples & memory tricks in the app
105 questions laddered from warm-up to topper-level, each with an explanation. A taste:
Two shapes are laid one on top of the other and neither leaves a gap nor sticks out anywhere. Shapes that fit like that are called
Beginnercongruent
They are geometric twins.
Two shapes are to be tested, and only one test settles the matter whatever they look like side by side. The real test is whether one can be
Beginnerlaid over the other exactly
With no gap and nothing sticking out.
When testing congruence, turning the second shape is
Intermediateallowed, and so is flipping
Position does not matter.
Two triangles have exactly the same shape but one of them has been drawn larger than the other. Such a pair is
Intermediatenot congruent
One is simply bigger than the other.
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