easy
163
4096
73
147
You have two hourglasses: one measures 7 minutes and the other 11 minutes. Using only these, measure exactly 15 minutes.
start both hourglasses at the same time, flip the 7-minute glass when it empties, and when the 11-minute glass finishes there will be 3 minutes left in the 7-minute cycle; flip it again to measure the remaining 4 minutes, totaling 15 minutes?
A plane crashes exactly on the border between the United States and Canada. Where do they bury the survivors?
you don’t bury survivors?
10000101-67
10000034
70-1
69
242
576
You have 8 identical-looking balls, but one is heavier than the others. Using a balance scale and only two weighings, determine the heavier ball.
What is: divide the balls into 3–3–2, weigh 3 against 3, and then weigh two from the heavier group (or the pair if the first weighing balances) to identify the heavier one?
Some months have 31 days, others have 30 days. How many months have 28 days?
all 12 months?
454-90
364
200*4
800
35
243
A man lives on the 10th floor. Every morning he takes the elevator to the 1st floor. But when he comes home, he rides only to the 7th floor and walks the rest of the way. Why?
he is too short to reach the button for the 10th floor, so he can only press up to the 7th?
If you have three apples and take away two, how many apples do you have?
What is: two apples (because you took them)?
33-33
0
400+218
618
166:2
83
You have three switches in one room and three light bulbs in another room. You can enter the bulb room only once. How can you determine which switch controls which bulb?
turn one switch on for several minutes, turn it off and turn on the second switch, then enter the room—the lit bulb is the second switch, the warm bulb is the first, and the cold dark bulb is the third?
Before Edmund Hillary and Tenzing Norgay climbed Mount Everest in 1953, who was the first person to reach the top?
no one — it had not been climbed yet?
4545-0
4545
324-444
-120
1617:22
73.5
There are 100 prisoners and 100 boxes, each box containing a prisoner’s number. Each prisoner may open only 50 boxes. If every prisoner finds their own number, they all survive. What strategy gives about a 30% chance of success?
What is: the cycle-following strategy, where each prisoner starts with the box labeled with their own number and then opens the box corresponding to the number found inside the previous one?
A rooster lays an egg on the roof of a barn exactly on the ridge. Which side does the egg fall on?
roosters don’t lay eggs?
566-000
566