Written down it says I + IX = X, which is right. Turn the paper round and it says X = XI + I, which is wrong.
Two mathematicians sit facing each other across a table. Between them is a sheet of paper with a short sum on it, written in Roman numerals. One says the sum is right. The other says it’s wrong. They’re both correct. How?
Give me a hintThe hint
Where is each of them sitting?