You've replaced Homer Simpson at the nuclear power plant and, lucky for you, now the threat of a meltdown is imminent. One of the 12 critical fuel rods is damaged: although it looks the same as the other 11, it doesn't weigh the same, a potentially devastating flaw. All the power in the plant has failed (doh!) and all you have is a balance scale for comparing the weight of the fuel rods on which you can put any number of rods on either side. But time is of the essence; you have at most three weighings to determine which rod is damaged and, to calculate radiation risk, whether it is heavier or lighter than the others. How can you save Springfield?

Scroll Down For Hint

Hint #1: You have to first weigh four of the rods against another set of four, leaving four to the side.

Scroll Down for Hint #2

Hint #2: You will need to reuse some of the nuclear rods that you have already deemed safe in order to properly use the balance.

Still stuck? Scroll down for a link to the answer.

Answer: It’s a bit complicated. Go here (alas, pool balls instead of nuclear rods):