Welcome to my brain teaser page, where you’ll find a collection of challenging and entertaining puzzles that will put your mind to the test! My brain teasers come in various forms, including riddles, logic puzzles, and math problems, and are designed to exercise your critical thinking, problem-solving, and creative thinking skills.
Whether you’re looking for a quick mental workout during your coffee break, a fun challenge to do with friends, or a way to impress your coworkers with your intelligence, our brain teasers are sure to fit the bill. Some of them are easy, some are hard, and some will leave you scratching your head for hours.
So, get ready to flex your mental muscles, think outside the box, and have fun with our brain teasers. Don’t worry if you can’t solve them all – the goal is to exercise your brain, not to be perfect. Can you Solve them all? Enjoy the challenge!
There are 100 doors in a row, all initially closed. You make 100 passes by the doors starting with the first door every time. The first time through, you visit every door and toggle the door (if the door is closed, you open it, and if it is open, you close it). The second time you only visit every 2nd door (door #2, #4, #6, …). The third time, every 3rd door (door #3, #6, #9, …), etc, until you only visit the 100th door on your 100th pass.
Which doors are open after your last pass?
You have a 3-gallon jug and a 5-gallon jug, and an unlimited supply of water. You need to measure exactly 4 gallons of water. How can you do it using only these two jugs?
You are in a room with three light switches, each of which controls one of three light bulbs in the next room. You cannot see the next room from where you are, and once you enter the next room, you cannot go back. You are allowed to flip the switches as much as you want, but you can only enter the next room once. How can you determine which switch controls which light bulb?
Suppose there are 100 people in a room, each wearing a shirt with a unique number from 1 to 100 on the front. You are blindfolded and cannot see the numbers on the shirts. Your goal is to group the people into three sets, each containing at least one person, such that the sum of the numbers on the shirts in each set is the same.
Here are the rules:
- You can only ask questions of the form “Is person X in set Y?” and receive a yes or no answer.
- You cannot ask for the numbers on the shirts or any other information about the people.
- You can only ask a limited number of questions, but you can group people into sets as many times as you want.
What is the minimum number of questions you need to ask to achieve your goal?
A farmer has ducks that lay eggs every day. Each duck lays a different number of eggs each day. One day, the farmer collects all the eggs and puts them in a basket. He then discovers that if he groups the eggs by threes, there is one egg left over. If he groups the eggs by fours, there is one egg left over. If he groups the eggs by five, there is one egg left over. Finally, if he groups the eggs by six, there is one egg left over. What is the smallest number of ducks that the farmer could have?
A pet store has cats and dogs available for adoption. One day, a customer buys 3 cats and 5 dogs for $250. Another customer buys 5 cats and 2 dogs for $170. What is the cost of one cat and the cost of one dog?