For each one, first the puzzle is posed for you to solve within a recommended time. A detailed systematic solution then follows.
Matchstick puzzles, riddles, math puzzles, logic puzzles, river crossing puzzles, ball weighing puzzles are some of the categories.
The full list of all brain teasers with solutions is available in the link,
Challenging brain teasers with solutions: Long list.
This will always be the most up-to-date list with the brain teasers classified into categories that can be browsed separately.
A milkman has to deliver 1 quart of milk each to a 4 pint and a 5 pint jug from his two 10 gallon filled up milk cans. Time to solve 20 mins.
Peter and Paul are always lying and truth-telling twins. You ask one of them, "Is Paul the lying one?" And he answers, "Yes." Whom did you ask the question?
Airplane Riddle of Flying Around the World: One airport can be used by airplanes. An airplane carries enough fuel to fly halfway across the globe...
How many addition signs should be put between digits of 987654321 to equal 99? Where should they be placed? Time to solve 10 minutes.
Cherry in the glass puzzle: Move 3 matchsticks to take the cherry out of wine glass. Second puzzle is harder: Move 2 matchsticks to take the cherry out.
Move 2 matches to make 7 squares and move 8 to make 6 squares. Total time to solve the pair of challenging matchstick puzzles is 20 minutes.
Matchstick tower puzzle: Move 4 matches to invert the tower. This is a different type of matchstick puzzle that is challenging to solve in 20 minutes.
9 squares puzzle: Find area of rectangle with 9 gradually smaller squares inside it and the side length of smallest square 3 units. Time 30 minutes.
Surely you can solve the 3 digit number puzzle in 20 mins if you approach the puzzle with systematic problem solving techniques.
Find area of equilateral triangle if side length of smallest of 3 squares inscribed in the triangle on top of each other is 1. It needs a bit of math.
