Which One Doesn’t Belong?

upper left: white isosceles triangle, pointing down<br />
upper right: nearly white, regular hexagon that is a little bit too wide<br />
lower left: white obtuse scalene triangle, pointing up and to the left<br />
lower right: shaded scalene right triangle, pointing to the right

shapes 1

by Mary Bourassa

upper left: 3<br />
upper right: 27<br />
lower left: 123<br />
lower right: 31

shapes 2

by Mary Bourassa

upper left: shaded circle<br />
upper right: white, wide ellipse<br />
lower left: white, regular dodecagon<br />
lower right: white semi-circle, resting on its flat side

shapes 3

by Mary Bourassa

upper left: a pink heart with a red outline<br />
upper right: A yellow star<br />
lower left: a bright green arrow made of a triangle stacked on a rectangle, each with its own red border<br />
lower right: a white, regular dodecahedron

shapes 4

by Isabelle Bourassa

upper left: a right triangle with legs 2 and x, and angle 30°<br />
upper right: right triangle with leg 2, hypotenuse 5, and angle not between them x°<br />
lower left: right triangle with legs 2 and 3, and hypotenuse x<br />
lower right: right triangle with leg 4, hypotenuse x, and non-included angle 22°

shapes 5

by Rachel Fruin

upper left: a sierpinski triangle upper right: a circular fractal-ish shape with six-fold symmetry lower left: a colored-in Koch snowflake lower right: a fern-like fractal, curving gently up and to the left

shapes 6

by Joshua Greene

upper left: a four-loop clover in bright red<br />
upper right: a cardioid in bright red, with a tiny interior loop at the top<br />
lower left: a cardioid in bright red, with a cusp at the bottom<br />
lower right: a three-loop clover

shapes 7

by Joshua Green

upper left: a rectangle with diagonals drawn in<br />
upper right: a square with diagonals drawn in<br />
lower left: an isosceles trapezoid with diagonals drawn in<br />
lower right: a non-rectangular parallelogram with diagonals drawn in

shapes 8

by Tina Palmer

upper left: a pattern block design with three lines of symmetry, and a hexagon at the center<br />
upper right: A pattern block design with a horizontal line of reflection<br />
lower left: A pattern block design, sketched on paper with pencil, with both a horizontal and a vertical line of symmetry<br />
lower right: A pattern block design with a square at the center, and four lines of symmetry

shapes 9

by Christine Corso

upper left: a cube<br />
upper right: a triangular prism, resting on a rectangular face<br />
lower left: a cylinder, lying on its side<br />
lower right: a rectangular prism, oriented like a shoebox with face of largest area as base

shapes 10

by Bryan Anderson

upper left: a square pyramid<br />
upper right: a cone, pointing up<br />
lower left: a trapezoidal prism, resting on a trapezoidal base<br />
lower right: an oblique cylinder, resting on a circular base and leaning to the left.

shapes 11

by Bryan Anderson

Four images composed of sections of a plane tiled with pattern blocks, using yellow hexagons, orange squares, and off-white diamonds.<br />
upper left: a wallpaper like pattern<br />
upper right: a pattern with imperfect rotational symmetry; roughly twelve-fold, but the center lacks that symmetry<br />
lower left: A seemingly arbitrary collection where the upper left of the design is much more dense with orange squares, and the lower extreme much more dense in yellow hexagons<br />
lower right: another wallpaperish pattern with flowers of four hexagons at jaunty angles, and separated by collections of squares surrounding a diamond.

shapes 12

by Simon Gregg

All four images are composed of congruent green triangles and congruent white diamonds, arranged to form a dodecagon<br />
upper left: The design has six triangles at the center, and rotational, but not reflection, symmetry<br />
upper right: the diamonds are in a star at the center, the triangles fill in the gaps<br />
lower left: four triangles and four diamonds at the center, and a rotaional symmetry pattern ensues<br />
lower right: four triangles and four diamonds are at the center, with a horizontal line of symmetry to the overall design

shapes 13

by Daniel Ruiz Aguilera

All four images are composed of congruent green triangles and congruent white diamonds, arranged to form a dodecagon<br />
upper left: The design has a rougly vertical line of symmetry, through a line of triangles.<br />
upper right: In this design, the line of symmetry runs upper left to lower right, through the centers of some diamonds and triangles. the design has an overall floral like feel.<br />
lower right: This design is a little more chaotic; as though someone took the one in the upper right, rotated it 90 degrees, and then mixed up the upper half so that it is no longer symmetric.<br />
lower right. This design has two triangles and eight diamonds at the center, and 180° rotational symmetry, but no line of symmetry.

shapes 14

by Simon Gregg

upper left: a horizontal ray, pointing to the right, on a green background.<br />
upper right: a horizontal line segment with a midpoint indicated, on a green background.<br />
lower left: A vertical line segment on a green background.<br />
lower right: a horizontal line segment on a yellow background.

shapes 15

by Ethan Rioux

upper left: an equilateral triangle, with one side labeled "4".<br />
upper right: A rhombus at a jaunty angle. One side is labeled "3", and the diagonals are drawn in.<br />
lower left: A rectangle in standard orientation with diagonals drawn in. One side is labeled "4" and an adjacent side is labeled "2".<br />
lower right: A pentagon with diagonals drawn in; one side is labeled "2".

shapes 16

by Michael Rubin

upper left: A blue rectangle with a large rectangular hole in the middle.<br />
upper right: A rectangle with upper left and lower right corners lopped off, forming an irregular hexagon.<br />
lower left: An isosceles trapezoid with horizontal parallel sides.<br />
lower right: An irregular trapezoid with vertical parallel sides.

shapes 17

by Mandy

upper left: green square.<br />
upper right: mauve circle.<br />
lower left: white rectangular prism.<br />
lower right: red irregular pentagon that looks like a rectangle with a corner lopped off.

shapes 18

by Noam Szoke

Four subdivided equilateral triangles.<br />
upper left: subdivided with two line segments parallel to one of the sides, and equally spaced.<br />
upper right: Subdivided into four congruent smaller equilateral triangles.<br />
lower left: Subdivided into three congruent kites. Also, this is the only one of the triangles that is pointing down.<br />
lower right: subdivided into three congruent irregular hexagons, each of which looks a bit like the letter J

shapes 19

by Erick Lee
link to more info

upper left: a pink isosceles triangle with base labeled "5" and height labeled "8".<br />
upper right: A green scalene triangle with base labeled "4" and height labeled "9".<br />
lower left: An isosceles right triangle with one leg labeled "6".<br />
lower right: A rectangle with base labeled "6" and height labeled "3".

shapes 20

by Chris Bolognese

Four expertly lit, digitally rendered solids. upper left: a cone upper right: a cube lower left: a cylinder lower right: a sphere

shapes 21

by Nat Banting

upper left: four interlocked puzzle pieces.<br />
upper right: a five by five grid of interlocked puzzle pieces, arranged as a completed jigsaw puzzle with straight borders.<br />
lower left: A three by three grid of interlocking puzzle pieces, arranged as though in the center of an incomplete jigsaw puzzle.<br />
lower right: Four corner puzzle pieces, not interlocked, but ready to assemble to make a square with no interior pieces. These pieces rest on a dark background.

shapes 22

by Elizabeth Gartland

Four hearts. upper left: Dark purple, with pointy end pointing to the right. upper right: Smaller and light purple, in the standard heart orientation. lower left: light purple, with pointy end point to the right. lower right: light green, in the standard heart orientation.

shapes 23

by Kimberley Craig

Four stars. upper left: four-pointed and yellow. upper right: five-pointed and magenta. lower left: six-pointed, small and yellow. lower right: eight-pointed and yellow.

shapes 24

by Kimberley Craig

upper left: a 4 cm by 3 cm rectangle.<br />
upper right: An isosceles trapezoid with sides 6, 4, 4, and 2 cm. The height is 3 cm.<br />
lower left: A dart with sides 3.8 and 3.2 cm. The interior diagonal is 2 cm; the external diagonal is 6 cm.<br />
lower right: a triangle with base 6 cm. The other two sides 4 cm. The height is 2 cm.

shapes 25

by Phil Aldridge