Puzzles are usually asked in interviews to see how you go about solving a tricky problem. Here are some of the puzzles which are logical, not tricky.
1. Divide the cake
You have a birthday cake. You have to divide the cake into 8 equal pieces. In how many cuts can you do it?
Try to divide the cake in minimum cuts.
Cut the cake in 4 pieces using 2 cuts- one horizontally down the center of the cake and the other vertically down the center of the cake.
Take all 4 pieces and arrange them into stack.
Now in 3rd cut, divide that stack in half.
2. Mislabeled jar puzzle
You have 3 jars which are mislabeled. 1st jar contains red balls, 2nd jar contains blue balls and the 3rd one contains both red and blue balls.
What is the minimum number of balls that you have to pick and from which jar to label them correctly?
Assume the balls are identical in shape and size.
Pick a ball from the 3rd jar. Suppose the ball is red, then 3rd jar contains only red balls (as it is mislabeled as mixture, so it should either contain red balls or blue balls.)
So the 3rd jar is labeled as RED.
Now the 2nd jar which is mislabeled blue, can not be red (already found). So the 2nd jar should be labeled as MIXTURE.
And the 1st jar is labeled as BLUE.
3. Minimum cut puzzle
Suppose you have a gold rod and you pay 1/5th of rod each day to someone who works for you.
What is the minimum number of cuts to divide the rod so that you pay him 1/5th each day?
Suppose the rod is 5 m long.
Cut it 2 times- first 1 meter from 5 m rod and second 2 meters from 4 m rod.
Now you have 3 pieces- one of 1-meter and two of 2-meters.
On 1st day- give him 1 meter piece. Now you have two 2-meter rods.
On 2nd day- give him 2 unit piece and take back 1 meter piece. Now you have one 1-meter rod and one 2-meter rod.
On 3rd day- give him 1 unit piece. Now you have one 2 meter rod.
On 4th day- give him 2 unit piece and take back 1 unit piece. Now you have one 1 meter rod.
On 5th day- give him remaining 1 unit piece.
4. Minimum distance
A lizard is present in one corner of a 10*10*10 feet house. An insect is present in diagonally opposite corner of the room (with respect to lizard).
Find the minimum distance the lizard has to cover to catch the insect.
Answer: 22.4 feet
The minimum distance would be the diagonal, but the lizard can’t fly. It can only go through the wall.
So the distance would be the diagonal of a wall which is 10 feet high and 20 feet wide.
Distance= (10^2 +20^2)^0.5 = 22.36 feet
Recently I attended a get-together. I counted the number of handshakes that were exchanged. There were 28 altogether.
Can you tell me how many guests were present?
Each person will shake hands with everyone except themselves. So for n persons=n(n-1)
But one handshake allows 2 people to shake hands,so total handshakes =(n(n-1))/2
so here n^2 – n=56