Tangram (Plastic) for School Maths Lab

Quick Answer: Tangram (Plastic) is the seven-piece square dissection puzzle made from rigid plastic, giving flat pieces with firm straight edges. Maths labs use the plastic tangram beyond picture puzzles, for fractions of a whole, angles of 45°, 90° and 135°, similar triangles and polygon challenges.

Geometry Hidden in Seven Pieces

Every angle in a tangram measures 45°, 90° or 135°, and every piece can be built from the same small right isosceles triangle. Rigid plastic keeps those edges straight and the corners sharp, so students can trace pieces accurately, measure their angles with a protractor and place them edge to edge without the gaps that softer materials leave.

Fractions of the whole square follow directly. Each large triangle is one quarter of the square; the medium triangle, the square piece and the parallelogram are one eighth each; and each small triangle is one sixteenth. Students can check that 1/4 + 1/4 + 1/8 + 1/8 + 1/8 + 1/16 + 1/16 adds to 1, which links the puzzle to adding fractions with different denominators.

The three sizes of triangle are all similar, which makes the set a hands-on route into similarity: a large triangle’s legs are twice as long as a small triangle’s and its area four times as large, while the medium triangle’s legs are √2 times as long. A classic challenge for older students is to find the thirteen convex shapes that can be made with all seven pieces.

Specifications

Care & Handling

• Wash plastic tangram pieces in lukewarm soapy water and dry them flat; very hot water can warp thin plastic.
• Keep each set of seven in its own bag or box, ideally colour-marked, so pieces from different sets do not mix.
• Check for cracked corners, which spoil tracing accuracy and can be sharp.

Applications

• Measuring and classifying the angles of each piece with a protractor
• Writing each piece as a fraction of the whole square and checking that the fractions add to 1
• Comparing the three similar triangles to connect length ratio and area ratio
• Tracing pieces to build and record polygons, including the convex-shape challenge

Why Choose LabEquip

Middle and secondary school teachers pick the plastic set when the tangram is used as a geometry tool rather than only a puzzle. Younger classes may prefer the softer Foam Tangram; both sit in the Mathematics School Lab Products range, and class-set quantities can be arranged through the contact page.

Frequently Asked Questions

What fraction of the square is each tangram piece?

Taking the whole square as 1, each large triangle is 1/4, the medium triangle, square and parallelogram are 1/8 each, and each small triangle is 1/16. Adding all seven gives exactly 1, which is a useful check on fraction addition.

Which angles appear in the tangram pieces?

Only three angles occur: 45°, 90° and 135°. The triangles each have one right angle and two 45° angles, the square has four right angles, and the parallelogram has two 45° and two 135° angles.

Are the tangram triangles similar?

Yes. All five triangles are right isosceles triangles, so they have the same angles and are similar. The large triangle has legs twice as long as a small one and four times its area, and the two triangles of each size are congruent.

How many convex shapes can be made with all seven pieces?

Thirteen: one triangle, six quadrilaterals (among them the square, a rectangle, a parallelogram and trapezia), two pentagons and four hexagons. Searching for all thirteen is a good extended task and shows how many arrangements fail to be convex.

Why use plastic rather than a paper tangram?

Paper tangrams bend, tear and develop fuzzy edges after a few lessons. Rigid plastic pieces keep straight edges and sharp corners, so they can be traced and measured accurately and reused year after year.

Can plastic tangram pieces be washed?

Yes. Wash them in lukewarm water with a little detergent, rinse and let them dry flat. Avoid dishwashers and very hot water, which may warp thin plastic pieces.

Last Updated: September 2026