"A tray strewn with dust or sand, used in ancient times for calculating. A contrivance for calculating,…

"Abacus is a Latin term applied to an apparatus used by the Chinese for facilitating arithmetical operations,…

Two Chinese men use the abacus to calculate for their business. "The abacus was one of the earliest…

"That point in which a right line drawn from the eye parallel to another given right line cuts the picture…

Used in businesses and bookkeeping, the adding machine was a device used for calculations. "One of the…

"It is found that the cord covering the curved surface is twice as long as the one covering the flat…

"The bases of the pyramids are considered as forming the surface of the sphere, while the altitude of…

Illustration of the three bears with three chairs that can be used to write mathematics story problems…

Illustration of children sitting on a bench and standing that can be used to write mathematics story…

Illustration of a child holding blocks that can be used to write mathematics story problems involving…

Illustration of a child counting books by twos that can be used to write mathematics story problems…

Illustration of 20 chicks that can be counted by twos. It can be used to write mathematics story problems…

Illustration of children playing darts that can be used to write mathematics story problems involving…

Illustration of a child buying doll clothes. It can be used to write mathematics story problems involving…

Illustration of a child buying doll toys. It can be used to write mathematics story problems involving…

Illustration of woman selling food in dozens that can be used to write mathematics story problems involving…

Illustration of a 6 toy elephants and a toy man that can be used to write mathematics story problems…

"In geometry, a curve generated by the motion of a point on the circumference of a circle which rolls…

"Epicycloidal wheel, a wheel or ring fixed to a framework, toothed on its inner side, and having in…

"Equipotential Lines about two similarly electrified spheres, A and B, the quantities of electricity…

Illustration of 6 children playing a game that can be used to write mathematics story problems involving…

"A piece of a parallelogram left after a similar parallelogram has been removed from a corner of it.…

Illustration of a child buying groceries. It can be used to write mathematics story problems involving…

Illustration of a jack-in-the box and 2 dolls. It can be used to write mathematics story problems involving…

Illustration of a child holding a kite that can be used to write mathematics story problems involving…

Illustration of Little Bo Peep and sheep. It can be used to write mathematics story problems involving…

Illustration of 2 children measuring liquids in pints and quarts. It can be used to write mathematics…

Illustration of 2 children comparing multiplication flash cards. It can be used to write mathematics…

Illustration of children holding number cards that can be used to write mathematics story problems involving…

Illustration of a child with 8 quarts and 1 peck. He is using the baskets to practice measuring. It…

Visualizing measurement with different containers that hold one pint and one quart.

Three students work from using dots as counters in columns (left) to writing the symbolic number (right).

Illustration of three rabbits and a carrot that can be used to write mathematics story problems involving…

Illustration of two rabbits and 8 carrots that can be used to write mathematics story problems involving…

A rhomboid is a parallelogam whose opposite sides are equal, and whose angles are not right angles.

A right-angled triangle is any triangle having one right angle. The side opposite the right angle is…

Illustration of cards that can be used for a matching game with Roman numerals, English numerals, and…

"In geometry, certain transcendental curves having, in polar coordinates, equations of the form ρ…

"In geometry, certain transcendental curves having, in polar coordinates, equations of the form ρ…

"In geometry, certain transcendental curves having, in polar coordinates, equations of the form ρ…

"In geometry, certain transcendental curves having, in polar coordinates, equations of the form ρ…

Illustration of a child measuring with rulers that can be used to write mathematics story problems involving…

Illustration of two children holding rulers that can be used to write mathematics story problems involving…

Illustration of children holding rulers that can be used to write mathematics story problems involving…

"Nodal Cubic, with four primary lines and their satellite. In the diagram, ABC is the satellite line.…

"In geometry: (a) A plane figure inclosed between the arc of a circle, ellipse, or other central curve…

Illustration of a child reading at school at 10:00. It can be used to write mathematics story problems…