The slope of perpendicular line to the a given line with a known slope is the opposite inverse of that slope. An opposite inverse is the number written as fraction flipped around and its sign changed. (negatives become positives and positives become negatives)
You could roll a 6-sided die 3 times to simulate this. This is a good simulation because it has one side for each possible tool, and each roll is independent, just as selecting the tool with replacement would be.
