Humble Pi: When Math Goes Wrong in the Real World

by Matt Parker

If you just enter = 0.5 − 0.4 − 0.1 into Excel, it will get it right. It knows that the total to subtract of 0.0111111 . . . should be exactly ½. However, if you enter = (0.5 − 0.4 − 0.1)*1, that freezes the error in place.