Many efforts at curriculum reform concentrated on high school teaching. Old forms of apparatus became more widely available. University professors worked with teachers to try out new approaches to teaching that emphasized the theoretical beauty of mathematics rather than its practical applications.

## Demonstration Slide Rule by Keuffel & Esser, 1967

The slide rule is an instrument used to assist in multiplication, division, and other mathematical operations. Widely used in American engineering schools from about 1900, it slowly diffused into high schools and lower grades. Slide rule makers also sold oversized examples for instruction. The Winchester-Thurston School, a girl's high school in Pittsburgh, purchased this slide rule for one of its classrooms.

## UICSM Programmed Textbook, 1963

## Blackboard Compasses, about 1950

## Experimental Units of Minnesota School Mathematics Center, 1963

Students studied topics such as information theory, computer logic, set theory, calculus, and vector analysis, which had not been part of the standard high school curriculum. Students also had the opportunity to write and run programs for a CDC 160 computer. At the time, computers were extremely large and expensive, and the opportunity to use one was an unusual event. Rosenbloom and one of his colleagues later wrote a textbook that was used in many colleges.

## Game of WFF'N PROOF, 1969

Allen and his colleagues hoped to develop games and other materials that would offer a ways to convey logical principles. In 1961 and 1962 they released different versions of WFF'N PROOF, a series of 21 games designed for learners from young children to adults. Allen's brother Robert tried out the games with students in California and Florida. His success led Allen and others to revise WFF'N PROOF further.