The RIDDLE quizzz

There are 10 people who are walking across the street. Only two of them have umbrellas. How do they get across?

You are trapped in a room with two doors. One door leads to certain death, and the other leads to freedom.

Two guards stand in front of the doors. One always tells the truth, and one always lies. You don’t know which guard is which.

You can ask only one question to one of the guards. What question do you ask to ensure you pick the door to freedom?

• You ask either guard:

  “If I were to ask the other guard which door leads to freedom, what would they say?”

  Then, take the door of which they point to.

• You ask either guard:

  “If I were to ask the other guard which door leads to freedom, what would they say?”

  Then, take the opposite door of what they point to.

• You ask either guard:

  “If I were to ask the other guard which door leads to freedom, what would they say?”

  Then, use your brain and break through the ceiling.

• You ask either guard:

  “If I were to ask the other guard which door leads to freedom, what would they say?”

  Then, don’t take any doors.

You are in a room with three light switches outside of another room. Inside that room is one lightbulb, but you cannot see it unless you open the door.

Each switch controls the lightbulb, but only one actually turns it on.

You can only enter the room once.

How do you determine which switch controls the lightbulb?

• 1. Turn OFF the first switch and leave it on for a few minutes.

  2. Turn OFF the first switch, then quickly turn ON the second switch.

  3. Immediately walk into the room.

• 1. Turn ON the first switch and leave it on for a few minutes.

  2. Turn OFF the first switch, then quickly turn ON the second switch.

  3. Immediately walk out of the room.

• 1. Turn ON the first switch and leave it on for a few minutes.

  2. Turn OFF the first switch, then quickly turn ON the second switch.

  3. Immediately walk into the room.

• 1. Turn ON the first switch and leave it on for a few minutes.

  2. Turn OFF the second switch, then quickly turn ON the first switch.

  3. Immediately walk into the room.

Answer explanation

• If the bulb is on, the second switch controls it.

• If the bulb is off but warm, the first switch controls it (because it was on earlier).

• If the bulb is off and cold, the third switch controls it.

You are in a post-apocalyptic world. You come across a deserted town with a single well. The well contains exactly 1 gallon of drinkable water, but you have only a 5-gallon jug and a 3-gallon jug.

There are no markings on the jugs, and you must measure exactly 1 gallon to survive.

How do you do it?

• 1. Fill the 3-gallon jug to the top.

  2. Pour the 3 gallons into the 5-gallon jug.

  3. Fill the 3-gallon jug again.

  4. Pour from the 3-gallon jug into the 6-gallon jug (which leaves exactly 1 gallon in the 3-gallon jug).

  5. Empty the 5-gallon jug completely.

  6. Pour the 1 gallon from the 3-gallon jug into the empty 4-gallon jug

• 1. Fill the 3-gallon jug halfway.

  2. Pour the 3 gallons into the 5-gallon jug.

  3. Fill the 3-gallon jug again.

  4. Pour from the 3-gallon jug into the 5-gallon jug until the 5-gallon jug is full (which leaves exactly 1 gallon in the 3-gallon jug).

  5. Empty the 5-gallon jug completely.

  6. Pour the 1 gallon from the 3-gallon jug into the empty 5-gallon jug

• 1. Fill the 3-gallon jug to the top.

  2. Pour the 3 gallons into the 5-gallon jug.

  3. Fill the 3-gallon jug again.

  4. Pour from the 3-gallon jug into the 5-gallon jug until the 5-gallon jug is full (which leaves exactly 1 gallon in the 3-gallon jug).

  5. Empty the 5-gallon jug completely.

  6. Pour the 1 gallon from the 3-gallon jug into the empty 5-gallon jug

• 1. Fill the 3-gallon jug to the top.

  2. Pour the 3 gallons into the 5-gallon jug.

  3. Fill the 3-gallon jug again.

  4. Pour from the 3-gallon jug into the 5-gallon jug until the 5-gallon jug is full (which leaves exactly 1 gallon in the 3-gallon jug).

  5. Empty the 2-gallon jug completely.

  6. Pour the 1 gallon from the 3-gallon jug into the empty 5-gallon jug

Answer explanation

• You only have two jugs, and neither has measurements.

• You must find a way to leave exactly 1 gallon without guessing.

• This is based on Diophantine equations (used in number theory).

You are in a 100-story building and have two identical eggs. The eggs will break if dropped from a certain floor or higher, but you don’t know which floor that is.

Your goal: Find the highest floor from which you can drop an egg without breaking it—using the fewest drops possible.

• 1. Instead of testing every floor one by one, start by skipping floors in intervals.

  2. Drop the first egg from floor 20, then 40, then 60, etc. (increasing by 10).

  • If it breaks, you know the correct floor is between the last safe floor and this one.

  3. Once an egg breaks, switch to one-floor increments with the second egg

• 1. Instead of testing every floor one by one, start by skipping floors in intervals.

  2. Drop the first egg from floor 5, then 10, then 15, etc. (increasing by 10).

  • If it breaks, you know the correct floor is between the last safe floor and this one.

  3. Once an egg breaks, switch to one-floor increments with the second egg

• 1. Instead of testing every floor one by one, start by skipping floors in intervals.

  2. Drop the first egg from floor 100, then 200, then 300, etc. (increasing by 10).

  • If it breaks, you know the correct floor is between the last safe floor and this one.

  3. Once an egg breaks, switch to one-floor increments with the second egg

• 1. Instead of testing every floor one by one, start by skipping floors in intervals.

  2. Drop the first egg from floor 10, then 20, then 30, etc. (increasing by 10).

  • If it breaks, you know the correct floor is between the last safe floor and this one.

  3. Once an egg breaks, switch to one-floor increments with the second egg