A good puzzle from Futility Closet.
You're on a drug regimen that requires you to take one pill a day from each of two bottles, A and B. One day you tap one pill into your palm from the A bottle and, inadvertently, two pills from the B bottle. Unfortunately the A and B pills are indistinguishable, and taking more than one B pill per day is fatal. And the pills are very expensive, so you can't afford to throw out the handful and start over. How can you arrange to take the correct dose without wasting any pills?