Calculator watch Calculator watch A calculator watch is a digital watch with a built in calculator, usually including buttons on the watch face. Calculator watches were first introduced in the 1970s and continue to be produced, despite falling from their peak popularity during the 1980s. The most notable brand is the Casio Databank series, though watches made by Timex were also popular. Most calculator watches contain only a few number of functions such as +, -, x, / and percents. However, there are several models with additional functions: scientific, including transcendent and trigonometry, in models Casio CFX-200, CFX-400, Citizen 49-9421, and also
QAMA Calculator QAMA Calculator The QAMA Calculator is a calculator that requires users to provide a reasonable estimate of the answer before the precise answer is delivered. QAMA stands for Quick Approximate Mental Arithmetic. Invented by Ilan Samson, it aims to get users to think first by estimating before they get the correct answer. Estimation is seen by many as an essential part of mathematics, and some believe that the presence and popularity of calculators could inhibit the use of estimation skills. A physical version of the calculator was released for sale in 2014, with apps for smartphones and tablets developed in