Sample Question #36 (brainteaser)

(The interviewer writes down the following equation on the whiteboard…)

XI + I = X

This is an equation expressed in Roman numerals. Imagine this equation is actually written out using sticks. Without touching or adding any stick, how can you make this equation true?

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Are the sticks metal sticks? I can use a magnet, right?

Nice try, Chris. 🙂 Those sticks are wooden sticks. More generally, you cannot move any stick (but this last condition is really a hint!).

move one stick to change XI to IX, which reads 9+1=10. Don’t understand the "cannot move" or "without touching" …

or, one could look at the equation upside-down, when it reads 10=9+1

XI = I + X ; atleast we can move other stuff around

ANSWER

The comment from 8/6/2007 is correct: you just look at the equation upside-down!