A. Ursula von der Leyen
B. Christine Lagarde
C. Elvira Nabiullina
D. Isabel Schnabel

A. Kyoto Protocol
B. Paris Agreement
C. Glasgow Pact
D. Copenhagen Accord

A. Apple
B. Samsung
C. Google
D. Huawei

A. Indonesia
B. Saudi Arabia
C. Mexico
D. Nigeria

A. France
B. Japan
C. Australia
D. USA

Puzzle: A triangle appears to be formed by rearranging 13 small pieces into a larger triangle, but one unit square seems missing. How?

Answer: The large triangle is not a true triangle; it’s slightly off due to different slopes of rearranged pieces. The illusion of a missing square arises from the area mismatch.

Puzzle: Three humans and three vampires must cross a river using a boat that holds two. Vampires can’t outnumber humans on either side. How can they cross?

Answer:

1. Two vampires cross, one returns.
2. Two vampires cross, one returns.
3. Two humans cross, one vampire and one human return.
4. Two humans cross, one vampire returns.
5. Two vampires cross, one returns.
6. Two vampires cross.

Puzzle: You have two eggs and a 100-floor building. You want to find the highest floor from which an egg can be dropped without breaking. What is the minimum number of drops needed?

Answer: 14 drops are required. Drop the first egg from floors 14, 27, 39, …, and so on. If it breaks, use the second egg to test each floor sequentially from the last safe floor. This ensures a minimal worst-case scenario.

Puzzle: An ant starts at a corner of a 1x1x1 cube. It can only move along edges. How many ways can it reach the opposite corner in exactly 6 moves?

Answer: There are 38 ways. The ant must make 3 moves in each axis direction, and the sequence can be arranged in multiple combinations (permutations of 3 moves in each direction).

Puzzle: You have 25 horses and a track that can race 5 horses at a time. What is the minimum number of races needed to determine the top 3 horses?

Answer: 7 races are needed:

1. Race 5 groups of 5 horses (5 races).
2. Race the winners (1 race) to find the fastest.
3. Take the top 2 from the winner’s race, plus the 2nd and 3rd from the winner’s first race, and race them (1 race) to find 2nd and 3rd place overall.

Puzzle: A farmer has 12 sheep, and all but 9 die. How many are left?

Answer: 9 sheep are left. The phrase “all but 9” means 9 survived.

Puzzle: You have two envelopes, each with money. One has twice as much as the other. You pick one and see $100. You can switch or keep. Should you switch?

Answer: There’s no advantage to switching. The expected value doesn’t change because if you switch, there’s an equal chance of doubling or halving your amount. The paradox challenges our intuitive grasp of probability.

Puzzle: At a four-way intersection, four traffic lights direct each way. Each light is green for 30 seconds, yellow for 5, and red for 30. How often are all lights red simultaneously?

Answer: The cycle repeats every 70 seconds. All lights are red simultaneously for 0 seconds because they change to green or yellow before all four can be red.

Puzzle: You meet two people at a fork in the road. One always lies, and the other always tells the truth. One path leads to safety, and the other to danger. What question do you ask to find the safe path?

Answer: Ask either, “If I asked the other person which path leads to safety, what would they say?” Take the opposite path of what they tell you. The liar will lie about the truth-teller’s answer, and the truth-teller will tell you the liar’s lie.

Puzzle:
A farmer must transport a fox, a chicken, and a sack of grain across a river. The boat can carry only two items, and the fox can’t be left alone with the chicken, nor the chicken with the grain. How does he do it?

Answer:

Take the chicken across.
Return alone.
Take the fox across, bring the chicken back.
Take the grain across.
Return alone, and take the chicken across.