Tangram Puzzles: Which Piece Is Missing?

Six figures are drawn on this 1st grade page, each built from six of the seven tangram pieces with the seventh left out. The gap is outlined in orange dashes so its exact shape is visible, and three chips stand beside it. The chips are drawn true to size against the figure, which matters: a small triangle and a medium triangle differ only by size, and the page expects that difference to decide the answer. Across the six cards the hole is a medium triangle, a small triangle, the square or the parallelogram.

Congruence is the whole lesson here. When a triangle is missing the page always offers the other triangle size as a rival, so a child who reads only the shape name picks wrong half the time and has to look at how long the sides are. The parallelogram is the sharpest card, because it is the one piece that cannot be turned over on the table: the chip that fits carries the same handedness as the hole, and its mirror image does not fit.

One sheet, six holes, eighteen chips. Note that the two large triangles never go missing on this face, so five of the seven pieces are in play rather than all seven. Use it after the shadow page, when a child can already build but has not yet had to argue that two shapes are the same. A cut set is useful but not needed: the chips are printed to size.