Chris and Lucy entered a building looking for Manuel. In a room they found a note and a lighted candle. Chris looked at the note and read it aloud:
“Hi! It’s 2:30, and I’m leaving to run some errands. I’ll be back in a couple of hours. BTW, the electricity is out, so I lit a candle for you. — Manuel.”
Then Lucy said, “I know how we can find out how long it’s been since he left! Look, the candle has been burning since he lit it and has a significant amount of wax that’s melted and dripped down. If we figure out what the rate is which the wax is melting and measure the amount of wax that has thus far dripped, we can work backwards to find out how long it has been since he left.”
Chris said, “Why waste your time? The note says he left at 2:30.” Lucy said, “Don’t believe everything you read.” Chris replied, “Look, I’ve known Manuel for a long time, and this is his handwriting. Don’t be ridiculous.”