Puzzles

A snail is at the bottom of a 20-foot well. Each day, it climbs up 5 feet, but at night, it slips back 4 feet. How many days will it take for the snail to reach the top of the well?

If 5 machines take 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?

I am an odd number. Take away a letter and I become even. What number am I?

You have two ropes. Each rope takes exactly 60 minutes to burn completely, but they burn at uneven rates. How can you measure exactly 45 minutes?

What comes next in the sequence: 1, 11, 21, 1211, 111221, 312211, ...?

A farmer has 17 sheep, and all but 9 die. How many are left?

You have 8 balls. One of them is slightly heavier than the others. What is the minimum number of weighings on a balance scale required to find the heavier ball?

There are three boxes. One is labeled 'Apples', another 'Oranges', and the third 'Apples and Oranges'. All labels are incorrect. You can pick just one fruit from one box to correctly label all three. Which box do you pick from?

A man is looking at a photograph of someone. His friend asks who it is. The man replies, 'Brothers and sisters, I have none. But that man's father is my father's son.' Who is in the photograph?

You have a 3-gallon jug and a 5-gallon jug. How can you measure exactly 4 gallons of water?