Calculators became portable during the 1970s following a breakthrough that enabled their development with just a few low-powered chips. In 1973, they also became affordable thanks in large part to Sinclair Cambridge, which produced a calculator for £29.95 (plus one in kit form for a fiver).
Calculators not only allowed adults to solve complex mathematical problems, but they were also encouraging children to test and improve their mental maths skills.
Cue ‘Little Professor’, a calculator that worked in reverse by displaying a series of sums on a red LED display and getting the user to answer them.
Little Professor was created by Texas Instruments and released in 1976, marketed as “the fun new way to learn arithmetic”.
The aim was to answer 10 equations correctly and get a perfect score. If the user got one wrong, “EEE” would display on the screen, prompting another try. Following the third wrong answer, the correct solution would appear and it would then move on to the next equation.
More than 16,000 problems were programmed into Little Professor and it could keep going for some time on its single 9-volt disposable battery.
To spice things up, there were four levels of problem difficulty, as well as a range of activities detailed in an accompanying booklet called Fun With Math Facts, some of which required two or more players.
The calculator proved so popular that, by 1977, it had sold more than a million units.
A second version of Little Professor was released in 1978 which moved some of the function keys around. Further modifications took place in 1980 and 1982, the latter replacing the LED display with LCD, and in the 2000s, a solar-powered version was introduced.
Little Professor is still sold today and there’s even an Android version to be enjoyed via Google Play.