The trouble with mathematics is that in general, in contrast to the real world, answers are either right or wrong, there’s no in between, so we were shocked and stunned to learn that Microsoft Corp’s Excel spreadsheet – all MS-DOS versions anyway – rounds percentages like 17.45 up to 18% rather than down to 17%, so that if you draw a pie chart with it, the percentages it shows don’t necessarily add up to 100: as the building engineer said, if the architect makes a mistake, there may be a puddle on the floor, if the engineer makes a mistake, the whole floor may vanish.
