A stumper of a puzzle‚ using only 4th grade math.
Effect: Using matches (or in our case - toothpicks), create the incorrect math equation 1+11+111=1111. Then challenge your friend to move only 1 match and make the equation true. Make sure to point out that the 4 matches on the right side of the equation are correct; it‚ only the left side that needs fixing. To be even more fair, point out that they can interpret the numbers as roman numerals, hash marks, or traditional Arabic numerals (in truth, all these extra options only serve to make the puzzle even harder).
Method: Take one of the matches from the 11 section, turn it 90 degrees and place it perpendicularly over the middle match in the 111 section. Properly spaced, the equation then appears as 1 + 1 + 1 + 1 = 1111!