"From Figure 4 he sees a parallelogram equal to a rectangle of the same base and altitude. Cut out and paste in rectangle form." -Foster, 1921

Area of Parallelogram

"From Figure 4 he sees a parallelogram equal to a rectangle of the same base and altitude. Cut out and…

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the trapezoid, and whose altitude is the same as that of the trapezoid." -Foster, 1921

Area of Trapezoid

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the…

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the trapezoid, and whose altitude is the same as that of the trapezoid." -Foster, 1921

Area of Trapezoid

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the…

"The triangle ABC is divided into 2 right triangles I and II. ABC is seen to be equal to 1/2 of the rectangle ABNO." -Foster, 1921

Area of Triangle

"The triangle ABC is divided into 2 right triangles I and II. ABC is seen to be equal to 1/2 of the…

"The child sees triangle ACB = triangle ADB, and that I + II = CA - DB; and so he sees that the area of triangle=1/2 area of rectangle whose base and altitude are the same as those of the triangles." -Foster, 1921

Area of Triangle

"The child sees triangle ACB = triangle ADB, and that I + II = CA - DB; and so he sees that the area…

"Fig. 3 shows triangle I = triangle II, III = IV, and so triangle ABC = 1/2 of rectangle ABDE. The fact is realized that the area of a triangle equals 1/2 the product of the base and altitude." -Foster, 1921

Area of Triangle

"Fig. 3 shows triangle I = triangle II, III = IV, and so triangle ABC = 1/2 of rectangle ABDE. The fact…

Illustration showing a circle with an inscribed and circumscribed quadrilateral.

Circle With Inscribed and Circumscribed Quadrilaterals

Illustration showing a circle with an inscribed and circumscribed quadrilateral.

Illustration of a composite figure made up of rings, rectangles, triangles, etc..

Composite Figure

Illustration of a composite figure made up of rings, rectangles, triangles, etc..

Illustration of a circle inside of 2 concentric rectangles whose vertices are connected by line segments.

Circle Inside Concentric Rectangles

Illustration of a circle inside of 2 concentric rectangles whose vertices are connected by line segments.

A regular body with six square faces; a rectangular parallelopiped, having all its edges equal.

Cube

A regular body with six square faces; a rectangular parallelopiped, having all its edges equal.

Illustration of 3 squares inscribed in an regular dodecagon. Each vertex of the dodecagon is also a vertex of one of the squares.

3 Square Inscribed In A Dodecagon

Illustration of 3 squares inscribed in an regular dodecagon. Each vertex of the dodecagon is also a…

Illustration of a square circumscribed about a regular dodecagon. This could also be described as a dodecagon inscribed in a square.

Square Circumscribed About A Dodecagon

Illustration of a square circumscribed about a regular dodecagon. This could also be described as a…

Illustration of a square inscribed in an regular dodecagon.  This could also be described as a regular dodecagon circumscribed about a square.

Square Inscribed In A Dodecagon

Illustration of a square inscribed in an regular dodecagon. This could also be described as a regular…

Illustration of 2 squares; one inscribed in a regular dodecagon and the other circumscribed about the same dodecagon.

Squares Inscribed and Circumscribed About a Regular Dodecagon

Illustration of 2 squares; one inscribed in a regular dodecagon and the other circumscribed about the…

Shading of the right and lower sides gives dimension to drawings.

Drawing Lines 2

Shading of the right and lower sides gives dimension to drawings.

2 rectangles that are similar figures

Similar Figures

2 rectangles that are similar figures

A flashcard featuring an illustration of a Parallelogram

Flashcard of a Parallelogram

A flashcard featuring an illustration of a Parallelogram

A flashcard featuring an illustration of a Pyramid with a Rectangular Base

Flashcard of a Pyramid with a Rectangular Base

A flashcard featuring an illustration of a Pyramid with a Rectangular Base

A flashcard featuring an illustration of a Rectangle

Flashcard of a Rectangle

A flashcard featuring an illustration of a Rectangle

A flashcard featuring an illustration of a Rhombus

Flashcard of a Rhombus

A flashcard featuring an illustration of a Rhombus

A flashcard featuring an illustration of a Trapezoid

Flashcard of a Trapezoid

A flashcard featuring an illustration of a Trapezoid

Showing different types of forms or shapes: rectangle, right triangle, acute triangle, and obtuse triangle.

Forms

Showing different types of forms or shapes: rectangle, right triangle, acute triangle, and obtuse triangle.

This fraction chart can be used for students to find A, B, and C in percentage. It can also be used to answer these questions (if it is 2.5 by 2 inches): "How many square inches in the entire figure? How many square inches in C? What part of a square inch is B? How large is A when compared to C? How large is B when compared to A? Into how many quarter-inch squares could you divide the whole figure?" -Foster, 1921

Fraction Chart

This fraction chart can be used for students to find A, B, and C in percentage. It can also be used…

An illustration of a rectangle shaped steel magnet with "consequent poles at a and b." -Century, 1889

Rectangle Shaped Steel Magnet

An illustration of a rectangle shaped steel magnet with "consequent poles at a and b." -Century, 1889

Labeled shapes showing various measures of form.

Measures of Form

Labeled shapes showing various measures of form.

An orthographic projection of a pyramid from three dimensional space into two dimensional space

Orthographic Pyramid Projection

An orthographic projection of a pyramid from three dimensional space into two dimensional space

Illustration of parallelogram AEFC drawn two different ways with base b and altitude/height a used to prove the area is aXb.

Area of a Parallelogram

Illustration of parallelogram AEFC drawn two different ways with base b and altitude/height a used to…

Parallelogram with dimensions drawn to show relationship to the area of a rectangle.

Parallelogram and Rectangle Relationship

Parallelogram with dimensions drawn to show relationship to the area of a rectangle.

Illustration of a decagonal prism with regular decagons for bases and rectangular faces. The hidden edges are shown.

Decagonal Prism

Illustration of a decagonal prism with regular decagons for bases and rectangular faces. The hidden…

Illustration of a right decagonal prism with regular decagons for bases and rectangular faces.

Decagonal Prism

Illustration of a right decagonal prism with regular decagons for bases and rectangular faces.

Illustration of a right decagonal prism with regular decagons for bases and rectangular faces. The prism is resting on its side, one of the faces.

Decagonal Prism Resting On Its Side

Illustration of a right decagonal prism with regular decagons for bases and rectangular faces. The prism…

Illustration of a swimming pool and water hose that is in the shape of a hollow regular decagonal prism with regular decagons on the ends/bases and square faces.

Swimming Pool Shaped Like A Decagonal Prism

Illustration of a swimming pool and water hose that is in the shape of a hollow regular decagonal prism…

"The prism of the first order consists of four rectangular vertical faces, each of which intersects the two horizontal crystallographic axes equally." — Ford, 1912

First order prism

"The prism of the first order consists of four rectangular vertical faces, each of which intersects…

Illustration of a hollow right heptagonal/septagonal prism with regular heptagons/septagons for bases and rectangular faces.

Heptagonal/Septagonal Prism

Illustration of a hollow right heptagonal/septagonal prism with regular heptagons/septagons for bases…

Illustration of a regular right heptagonal/septagonal prism with regular heptagons/septagons for bases and square faces. The hidden edges are shown.

Heptagonal/Septagonal Prism

Illustration of a regular right heptagonal/septagonal prism with regular heptagons/septagons for bases…

Illustration of a right heptagonal/septagonal prism with regular heptagons/septagons for bases and rectangular faces. The hidden edges are shown.

Heptagonal/Septagonal Prism

Illustration of a right heptagonal/septagonal prism with regular heptagons/septagons for bases and rectangular…

Illustration of a right heptagonal/septagonal prism with regular heptagons/septagons for bases and rectangular faces.

Heptagonal/Septagonal Prism

Illustration of a right heptagonal/septagonal prism with regular heptagons/septagons for bases and rectangular…

Illustration of a right hexagonal prism.

Hexagonal Prism

Illustration of a right hexagonal prism.

Illustration of a right hexagonal prism with hidden edges shown.

Hexagonal Prism

Illustration of a right hexagonal prism with hidden edges shown.

Illustration of a right hexagonal prism with a height less than the length of the edge of the hexagon.

Hexagonal Prism

Illustration of a right hexagonal prism with a height less than the length of the edge of the hexagon.

Illustration of a right hexagonal prism with a height greater than the length of the edge of the hexagon.

Hexagonal Prism

Illustration of a right hexagonal prism with a height greater than the length of the edge of the hexagon.

Illustration of a right hexagonal prism with hexagons for bases and square faces.

Hexagonal Prism

Illustration of a right hexagonal prism with hexagons for bases and square faces.

Illustration of a right hexagonal prism with hexagons for bases and square faces. The hidden edges are shown.

Hexagonal Prism

Illustration of a right hexagonal prism with hexagons for bases and square faces. The hidden edges are…

Illustration of a right hexagonal prism with hexagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the hexagon. The hidden edges are shown.

Hexagonal Prism

Illustration of a right hexagonal prism with hexagons for bases and rectangular faces. The height of…

Illustration of a right nonagonal prism with regular nonagons for bases and rectangular faces. The hidden edges are shown.

Nonagonal Prism

Illustration of a right nonagonal prism with regular nonagons for bases and rectangular faces. The hidden…

Illustration of a right nonagonal prism with regular nonagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the nonagon. The hidden edges are shown.

Nonagonal Prism

Illustration of a right nonagonal prism with regular nonagons for bases and rectangular faces. The height…

Illustration of a right octagonal prism with regular octagons for bases and rectangular faces. The hidden edges are shown.

Octagonal Prism

Illustration of a right octagonal prism with regular octagons for bases and rectangular faces. The hidden…

Illustration of a right octagonal prism with regular octagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the octagon. The hidden edges are shown.

Octagonal Prism

Illustration of a right octagonal prism with regular octagons for bases and rectangular faces. The height…

Illustration of a right octagonal prism with octagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the octagon.

Octagonal Prism

Illustration of a right octagonal prism with octagons for bases and rectangular faces. The height of…

Illustration of a right octagonal prism, with octagons for bases and rectangular faces, that is resting on its side (an edge). The height of the prism is greater than the length of a side of the octagon.

Octagonal Prism Resting On Side

Illustration of a right octagonal prism, with octagons for bases and rectangular faces, that is resting…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the pentagon. The hidden edges are shown.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is slightly greater than the length of a side of the pentagon. The hidden edges are shown.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is slightly greater than the length of a side of the pentagon.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the pentagon.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Prism with rectangular bases and cubes drawn in.

Rectangular Prism

Prism with rectangular bases and cubes drawn in.

Illustration of a non-regular decagonal prism in the shape of a star. Then ends/bases are made of star-shaped decagons and the faces are rectangular.

Star-Shaped Decagonal Prism

Illustration of a non-regular decagonal prism in the shape of a star. Then ends/bases are made of star-shaped…

Illustration of a non-regular decagonal prism in the shape of a star. Then ends/bases are made of star-shaped decagons and the faces are squares.

Star-Shaped Decagonal Prism

Illustration of a non-regular decagonal prism in the shape of a star. Then ends/bases are made of star-shaped…

Side view of a non-regular decagonal prism in the shape of a star. Then ends/bases are made of star-shaped decagons and the faces are squares.

Star-Shaped Decagonal Prism

Side view of a non-regular decagonal prism in the shape of a star. Then ends/bases are made of star-shaped…

Illustration of 2 right octagonal prisms with congruent bases, but different heights. The height of the smaller prism is one half that of the larger.

2 Octagonal Prisms

Illustration of 2 right octagonal prisms with congruent bases, but different heights. The height of…

Illustration of 2 Similar right octagonal prisms. The height and length of the edges of the smaller prism are one half that of the larger.

2 Similar Octagonal Prisms

Illustration of 2 Similar right octagonal prisms. The height and length of the edges of the smaller…