A barrel of water weighs 20 pounds. What must you add to it to make it weigh 12 pounds?

Why this works

This riddle plays with the idea of weight and the concept of adding something that actually reduces the weight. When you add holes to the barrel, you're not adding mass; instead, you're allowing the water to escape, which decreases the overall weight of the barrel and its contents. It's a clever twist on the expectation that adding something should increase weight, highlighting that sometimes the answer lies in removing rather than adding!