Texas Instruments SR-10 (1973)

Math classes were never the same after the introduction of TI's handheld calculators in the early 1970s. The $150 SR-10 debuted in 1973 and was the first affordable handheld to calculate reciprocals, square roots, and other slide-rule functions. The $170 SR-50 followed in 1974, adding trigonometric functions and a very cool 14-character LED display. The devices became so ubiquitous that math whizzes at the time were identified by the simple sobriquet "TIs." This TI site can tell you more about Texas Instruments calculators. Photo courtesy of the Vintage Calculators Web Museum.