21. Sal and Sam are brothers. Steve is Sal's son, and 12 years younger than his uncle. Sal is twice as old as Steve. Four years ago, Sal was the same age as Sam is now, and Sam was twice as old as his nephew. What are all the ages?
23. A man wanted to enter an exclusive club but did not know the password that was required. He waited by the door and listened. A club member knocked on the door and the doorman said, "twelve." The member replied, "six" and was let in. Another member came to the door and the doorman said, "six." The member replied, "three" and was also let in. The man thought he had heard enough and walked up and knocked on the door. The doorman said, "ten" and the man replied, "five." He was not let in. What should he have replied and why?
24. A snail is at the bottom of a well and wants to get out. He manages to crawl up the wall 3 feet each day, but at night he must rest ( after all that work during the day ) and so he slips back down 2 feet. If the well is 30 feet deep, How long will it take him to get out?
25. A builder needs 11 pounds of sand for his pool foundation. The sand supplier has a lot of sand, two large boxes on a balance scale, but only two weights: a 5 pound weight and a 4 pound weight. How can you measure exactly 11 pounds of sand without removing any sand from either of the boxes during the process?
26. Examine the following:
1 + 23 - 4 + 5 - 6 + 78 + 9 = 106
Notice that the digits 1 through 9 are used in order to arrive at 106. Using 1 through 9 in order, and using only addition or subtraction, create an equation that equals 100. There are many solutions.
27. You have two ropes. Each takes exactly 60 minutes to burn. They are made of different material so even though they take
the same amount of time to burn, they burn at separate rates. In addition, each rope burns inconsistently.
How do you measure out exactly 45 minutes?
29. I was relaxing on a park bench one day when I noticed there were ducks in the pond. I saw two ducks in front of a duck, two ducks behind a duck and one duck exactly in the middle of the other ducks. How many ducks were there?