Logic Puzzles with Solutions

Puzzle 1: How do you cut a circular cake into eight equal pieces in just 3 cuts?

Puzzle 2: You have a 3 liters and a 5 liters measuring jug. How are you going to get 4 liters from it?

Puzzle 3: You have 10 sets of 10 metal balls. You know the balls should weigh 10 g each. You know the balls in 1 set are exactly 1 g lighter. You are allowed to use an extremely accurate digital weighing scale only once. How do you determine which set of balls is lighter?

Puzzle 4: You have to fill the boxes with numbers from 1-8 by following below mentioned rules.
Rule 1: Predecessor and successor can’t be besides. Example if we take number 3 in any box, than neither side of 3 can have 2 or 4.
Rule 2: Predecessor and successor can’t be upside or downside. Example: if we take 3 in any box, then the box above can not have 2 or 4, similarly box below can not have 2 or 4.
Rule 3: Predecessor and successor can’t be diagonally either.

Puzzle 5: A Farmer had to cross a river, he had a Dog, a Chicken and some Corn. The Dog will bite the Chicken and the Chicken will eat the Corn if the Farmer is not around. The Farmer can only take 1 out of the 3 on the boat when crossing the river. How the Farmer can cross the river?

Puzzle 6: A dysfunctional family has to cross the river. On one side of the river are a Mother and 2 Daughters, Father and 2 Sons, the Maid and the Dog. There is a boat only big enough to hold 2 people (counting the dog as 1 person). Only the adults are capable of operating the boat. Everyone has to get to the other side, without anything bad happening.
Now the difficulties are : if the Dog is left with anyone and the Maid isn’t there to control him, he’ll bite. The Father can’t be left with any of the Daughters when the Mother isn’t there. Likewise, the Mother can’t be trusted alone with either of the Sons when the Father isn’t there.
Remember! only an adult can operate the boat, and the boat can’t drive itself.

Puzzle 7: A Cowboy need to cross the river with 4 Horses, he can only ride 1 and pull 1 when he cross. The Horses cross river at different speed, A require 1 minute, B require 2 minutes, C require 5 minutes and D require 10 minutes. The duration of the crossing will be the slowest Horse. If base on this logic, he cross with riding A and pulling the remaining Horses will be take 19 minutes in total as follows: A and B cross = 2 minutes, A come back = 1 minute, A and C cross = 5 minutes, A come back = 1 minute, A and D cross = 10 minutes. 2 + 1 + 5 + 1 + 10 = 19 minutes. But there is a way that he can complete the task at a shorter duration. Can you figure it out?

Puzzle 8: You got 8 eggs, 1 egg is spoil. The spoil egg is lighter than the other eggs. You can use a balancing scale only 2 times. Can you find out which egg is spoil?

Puzzle 9: You got 9 eggs, 1 egg is different. You do not know if the  egg is lighter or heavier than the other eggs. You can use a balancing scale only 3 times. Can you find out which egg is different?






Solution 1: Using 2 cuts to cut the cake into 4 equal pieces from the top, then using the 1 more cut to cut horizontally and you will get 8 equal pieces.


Solution 2: Fill the 5 liters jug. 
Pour 3 liters into the 3 liters jug with 2 liters remaining in the 5 liters jug. 
Empty the 3 liters jug. 
Pour the remaining 2 liters from the 5 liters jug into the 3 liters jug. Fill the 5 liters jug again. 
Pour 1 liter from the 5 liters jug into the 3 liters jug. 
Now the 5 liters jug will contains 4 liters.

Solution 3: Take 1 ball from the first set along with 2 balls from the second set and go on until you take 10 balls from the tenth set. If all the balls are 10 g you should get 550 g for 55 balls. If the weight is lighter by 1 g then it is the first set that is lighter, if the weight is lighter by 2 g then it is the second set which is lighter. By the reduce of weight you will be able to determine the set which is lighter.

Solution 4: 

Solution 5: The Farmer bring the Chicken cross the river.
The Farmer come back.
The Farmer bring the Dog cross the river.
The Farmer bring the Chicken back.
The Farmer bring the Corn cross the river.
The Farmer come back.
The Farmer bring the Chicken cross the river.

Solution 6: Maid and Dog cross first, and the Maid comes back.  
Maid and 1 Son cross, Maid and Dog come back. Father and another Son cross, Father comes back.
Mother and Father cross, Mother comes back.
Maid and Dog Cross, Father comes back.
Mother and Father cross, Mother comes back.
Mother and 1 Daughter cross, Maid and Dog come back.
Maid and another Daughter cross, Maid comes back.
Maid and Dog cross.

Solution 7: A and B cross = 2 minutes, A come back = 1 minute, C and D cross = 10 minutes, B come back = 2 minutes, A and B cross = 2 minutes. 2 + 1 + 10 + 2 + 2 = 17 minutes. 

Solution 8: Put 3 eggs on each side of the balance. 
If the scale tilt then the spoil egg is in the side which is higher. 
Take 2 eggs from the 3 eggs and put 1 egg on each side of the balance.
If the scale tilt then the spoil egg is in the side which is higher.

If the scale balance then the spoil egg is the remaining egg.
If the scale balance at first try then the spoil egg is in the remaining 2 eggs.
Take the 2 eggs and put 1 egg on each side of the balance.
The scale tilt with the spoil egg is on the side which is higher. 

Solution 9: Put 3 eggs on each side of the balance. 
If the scale tilt switch the remaining 3 eggs with the side which is higher.
If the scale still tilt, the egg is heavier and it is in the lower side.
If the scale balance, then the egg is lighter and it is in the set which you had just switch.
Take 2 eggs from the 3 eggs and put 1 egg on each side of the balance and you will be able to find the egg.