Difficulty – Hard

Hard brain teasers and puzzles

Difficulty - Hard, Rebus

Rebus Puzzle 4

What common word or phrase is this rebus referring to?

♣ OFFICE
♠ SCHOOL
♥ HOME
♦ STORE

Solution

Home is where the heart is

Difficulty - Hard, Interview Brain Teasers, Logic Puzzles

Hasan and Lauren attended a dinner party with 4 other couples. Since some people already knew some of the other guests, every person at the dinner party shook hands with every person they had not met before.

Lauren noticed that everyone else (excluding Lauren herself) ended up with a different number of handshakes!

Can you figure out how many people Hasan shook hands with?

Difficulty - Hard, Logic Puzzles

Tennis Match Mystery

Abe, Ben, and Catelyn were playing 1-on-1 tennis matches one afternoon. After each match, the winner stayed on the court and the loser was replaced by the person who sat out.

At the end of their session, Abe had played 8 matches, Ben had played 12 matches, and Catelyn had played 14 matches. Ben was particularly exhausted as he had played all of the last 7 matches.

Is it possible to figure out who played and who won in the 4th match?

Difficulty - Hard, Interview Brain Teasers

Same Place Same Time

You spend an entire day hiking up a mountain, and camp overnight at the top. The next day, you hike down the mountain along the same trail, starting around the same time you started the day before.

How likely is it that there is a point on the mountain that you passed at the exact same time on both days?

Chess, Difficulty - Hard

Bishop Holds Back the Pawns

A pretty challenging chess puzzle, because there isn’t a pre-determined number of moves. White to play and force a draw.

Difficulty - Hard, Trivia and Knowledge, Word Puzzles

Odd One Out

Which is the odd one out?

catwoman
deus ex machina
parishioner
pyromania
scuba

Difficulty - Hard, Interview Brain Teasers, Logic Puzzles

5 Pirates Puzzle

Five pirates are figuring out how to divide up a newly plundered treasure of 100 gold coins. From most senior to least senior: Pirate A, Pirate B, Pirate C, Pirate D, and Pirate E. The rules:

The most senior pirate must propose a distribution (for example, giving himself all 100 gold coins and 0 for everyone else), and then all the pirates must vote on it.
If at least half of the pirates vote for a proposal, the proposal is accepted and the gold is split according to that distribution.
Otherwise, if the proposal is rejected, the pirate that proposed it is kicked out, and this process repeats with the remaining pirates.
Each pirate’s main goal is to maximize the gold they receive (but a pirate that is kicked out gets no gold), but are also spiteful enough to prefer kicking out the other pirates, all else equal. The pirates are also distrustful of each other and will not make any side deals, so the distribution of an accepted proposal is final.

What is the greatest number of coins that Pirate A can distribute to himself?

This is a classic logic puzzle, occasionally encountered in tech interviews many years ago.

Preparing for a brain teaser interview? Check out our ultimate guide to brain teaser interviews.

Difficulty - Hard, Interview Brain Teasers, Probability

Wrong Seat Probability

There is a fully-booked flight with 100 seats. The first person decides to ignore the seat assignments, and sits in a random seat. Each subsequent person sits in their assigned seats if available, or sits in a random unoccupied seat if not.

What is the probability that the last person happens to find their assigned seat unoccupied?

Difficulty - Hard, Number Theory

Divisible by 100

Prove that for any set of one hundred whole numbers, either one of those numbers is divisible by 100 or the sum of a subset of those numbers is divisible by 100.

Difficulty - Hard, Patterns, Sequences, and Sets

Sequence Puzzle

Find the next two terms in this sequence:

10, 11, 12, 13, 14, 15, 16, 17, 21, 23, 30, 33, ?, ?