An old priest fell on a bottom of the well of a church.
The well is 20 inches deep.
At day time, the old priest climbs 5-inches but when at dark he slip back 4 inches.
In how many days priest will come out of the well?
The answer is 16 days.
Because, in 15 days, he will climb 15-inch and when he climbs 5 inch more, he will be out of the well 🙂