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

"To find the number of bushels of grain in a bin or box, multiply the length in feet by the height in…

This chart of comparisons can be used with the following questions: "Which line is twice B? Which two…

Illustration of a compass with one leg at point A on the line segment and the other at Point B.

Illustration of a compass with one leg at point O on the line segment and the other at Point M.

A small electric meter that measures electricity in units called kilowatts-hour. The first meter is…

A gas meter that measures feet of gas used. The first meter is in the thousands place and points just…

"Goniometer. An instrument for measuring solid angles, or the inclination of planes, particularly the…

"Goniometer. An instrument for measuring solid angles, or the inclination of planes, particularly the…

"Sextant. An important instrument of navigation and surveying, for measuring the angular distance of…

This table wheel would be used to practice the six tables. The teacher would rapidly point to the surrounding…