How a computer adds

Addition is the basis of all arithmetic in a computer.  Subtraction is adding a negative number, multiplication is repeated addition, and division is a combination of the others.  Of course, a computer uses binary numbers (digits 0 and 1 rather than digits 0 through 9).  This video describes how a binary adder circuit can be built using dominoes -- mirroring what actually happens in a computer.  The result is an easy-to-grasp description of computer arithmetic:  https://www.youtube.com/