Puzzles

                                 Most important puzzles for interview

1. Water Jugs

You have three water jugs, which can hold 8, 5 and 3 litres of water respectively. The 8 litres jug is full, and   the other two are empty.
Divide the water into 4 & 4 litres without using other jugs?

Answer:

Firstly fill 5 litres of jug from 8 litres.

Empty the 5 liter jug into the 3 liter jug - leaving 2 litres in the 5 litres jug.

Empty 3litres jug into 8litres jug. Now 8 liters jug have 6 litres water.

Empty the 5 litre jug into 3 litres jug. Now 3 litres jug have 2 litres water because 5 litre jug have only 2 litres water.

Again, fill 5 litres of jug from 8 litres.

 Fill 1 litre water into 3 litre jug-leaving 4 litres in the 5 litre jug.

Again, empty 3litres jug into 8litres jug.

Now 8 & 5 litres jug have 4, 4 litres water.

2. Person Height

In a room lives 4 brother of different height. Their average height is 74 inches, and the difference in height amongst the first three men is 2 inches. The difference between the third and the fourth man is 6 inches.

Can you tell how tall each brother is?

Answer:

1^st brother- 70 inches, 2^nd brother- 72 inches, 3^rd brother- 74 inches, 4^th brother- 80 inches.

3. Light Switches

Suppose that you are standing in a hall next to 3 light switches, which are all off. There is another room, where there are 3 light bulbs – each light bulb is operated by one of the switches in the hall. Because the light bulbs are in another room, you can not see them since you are standing in the hall. How would you figure out which switch operates which light bulb, if you can only go the room with the light bulbs only one time.

Answer

We know that light bulbs get hot when they are on.

So, if we turn one switch off  after 5 minutes turn the second one on, and leave the last one off the light bulb corresponding to the first switch will still be warm (even though it’s off), the bulb corresponding to the second switch will be on, and the bulb corresponding to the last switch will be off. This is enough information so that we can go into the attic only once and figure out which switch belongs to which light bulb.

4. Three Ant 

Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide?

Answer:

 So let’s think this through. The ants can only avoid a collision if they all decide to move in the same direction (either clockwise or anti-clockwise).

P(No collision) = P(All ants go in a clockwise direction) + P( All ants go in an anti-clockwise direction) = 0.5 * 0.5 * 0.5 + 0.5 * 0.5 * 0.5 = 0.25

5. Girl & Boys

A girl, a boy, and a dog start walking down a road. they start at the same time, from the same point, in the same direction. The boy walks at 5 km/h, the girl at 6 km/h.The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.

How far does the dog travel in 1 hour?

Answer:

10 km. Because the dog's speed is 10 km/h.

6. Maths

Make 1000 using eight 8s.

Answer:

 8 8 8

    8 8

       8

       8

 +    8

                 

  1000

  7.  A Problem Of Coins  

Can you place 10 coins in such a way that they lie in 5 straight lines and on each line there are 4 coins. There are at least two solutions.

Answer:

 


8. The Number Puzzle

There are two numbers with the difference of 3 between them and the difference of their square is 51.

Can you find the numbers?

Answer:

 

Let X -  one number

Let Y -  second number

X^2 – Y ^2=51    (1)

X – Y     =  3        (2)

Divide (1) & (2)

X + Y = 17  (3)

Add (2) & (3)

2X = 20

X = 10

Y = 7

9. Heart Apart

A man I know fell in love with a woman who lived 63 miles away. Finally he decided to propose marriage to his beloved and invited her to travel towards his place and offered to meet her en route and bring her home.

The man is able to cover 4 miles per hour to the woman 3 miles per hour.

How far will each have travelled upon meeting?

 Answer:

The man rate of speed is 4 miles an hour to the woman 3 miles and therefore their total rate is 7 miles an hour. Since they are 63 miles apart they can cover an average of 9 miles in one hour. Therefore  9* 4 = 36 miles travelled by the man and 9 * 3 = 27 miles the distance travelled by the woman.  

10. Exam: 

Two students appeared at an examination. One of them secured 9 marks more than the other and his marks was 56% of the sum of their marks. What are the marks obtained by them?

Answer:

 

42, 33

33 (+9) = 42

The 42+33= 75 and 56 % of 75 is 42

 

11. The Digital Game

There is a number, the second digit of which is smaller than its first digit by 4, and if the number was divided by the digit sum, the quotient would be 7.

Can you find the number?

Answer:

The number is 84.

 
12.  Spade For A Heart

Here is a spade

Can you cut the spade into three pieces that will fit together and form a heart?

Remember, no part of the material should be wasted.

Answer: