#21 - Friday Before Thursday Problem
When does Friday come before Thursday?
In the dictionary.
#22 - Light The Dark Room
You are in a dark room and want to see what is inside it. With you are a match, a candle, and a kerosene lamp. Which do you light first?
You have to Lit Match First , so you can light candle or lamp.
#23 - Light The Cords Problem
Your job is to measure 45 minutes, if you have only two cords and matches to light the cords.
1. The two cords are twisted from various materials and so their different segments can burn at different rates.
2. Each cord burns from end to end in exactly one hour.
Describe your way of measuring the 45 minutes.
Start fire on both ends of one igniter cord and on one end of the second igniter cord. The very moment the first cord (where both ends burn) stops burning (that is after 30 minutes), start fire on the other end of the second cord (otherwise it would burn another 30 minutes). Thus the second igniter cord burns just 15 minutes from then. And that is all together 45 minutes.
#24 - Ping Pong Problem
Your last good ping-pong ball fell down into a narrow metal pipe imbedded in concrete one foot deep.
How can you get it out undamaged, if all the tools you have are your tennis paddle, your shoe-laces, and your plastic water bottle, which does not fit into the pipe?
All you have to do is pour some water into the pipe so that the ball swims up on the surface.
Edit:
oysterboy22's wording solution: none of those random things are going to help you, but the whole point is the person thinks they have to use the tools, while what they really have to do is urinate in the hole.
#25 - Dish Full Problem
A Petri dish hosts a healthy colony of bacteria. Once a minute every bacterium divides into two. The colony was founded by a single cell at noon. At exactly 12:43 (43 minutes later) the Petri dish was half full.
At what time will the dish be full???
The dish will be full at 12:44.
Answer for old wording:
The saucer was half full at 11.59 - the next minute there will be twice as many of them there (so full at 12.00).
#26 - Escape from Killing Problem
A man aproaches you in a dark alley. He says, 'If you tell a lie, I will kill you with a knife. If you tell the truth, I will kill you with a gun.'
What do you say to stay alive?
Recognize that only declarative statements have a truth value.
Don't make a declarative statement; that way it won't be the truth or a lie.
Here are three possibilities:
[1] Remain silent. - or if you must say something, ask a question
[2] Why do you want to kill me? - or exclaim something:
[3] No! Please do not kill me!
#27 - Length Of Pole Problem
There is a pole in a lake. One half of the pole is in the ground, another one third is covered by water and eight feet is out of the water. What is the total length of the pole in feet?
48 feet
lets say x is the total height of the pole...
x/2 + x/3 + 8 = x
(3x+2x+48)/6 = x
5x+48 = 6x
x = 48
#28 - Dollar Problem
If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?
$13,212
#29 - Brick Problem
How many bricks does it take to complete a building that is 20 feet wide, 35 feet deep, and 14 feet tall made of brick?
One [the last one, which completes it].
#30 - Sum Problem
A lily pad doubles in size every day. If on the 60th day the pond is exactly filled with the lily pad, on what day is the pond exactly half covered?
Day 59. Since it doubles in size each day, the day before it exactly covers the pond it will half cover it.