There are many kinds of calculators, but most calculators have the same standard keys that allow users to complete a variety of calculations. The number keys and addition, subtraction, multiplication, division and equal ... More »

A product key refers to a unique 25 character alphanumeric code that is required to activate Microsoft Office 2013 after installation. The product key and its subsequent use in product activation allows Microsoft to veri... More » Technology Software

To use an annuity fund calculator, go to a financial website and enter the information required to perform the calculations. Annuity funds are investments that can create a stream of income, increase a person's retiremen... More » Math Math Calculators

A 10-key adding machine is a mechanical calculator used in companies and stores before there were electronic calculators. This machine can perform simple calculations, such as addition and subtraction of numbers. The ear... More »

An ERR:INVALID DIM error on a TI-84 calculator indicates that one or more STAT PLOTS is turned "on" but there are no values in the STAT lists. If the error occurs when trying to graph a function, then the error can be fi... More » Math Math Calculators

Solar-powered calculators work the same way that other calculators work but use solar cells for power instead of batteries. Solar cells, also known as photovoltaic cells, take the sun's energy and turn it into electricit... More »

Reliable and free online calculators can be found at, and, as of 2015. These sites provide various easy-to-use calculators for many different occasions. More » Math Math Calculators