Logic Riddles

#11 - River Riddle

Four people need to cross a dark river at night.They have only one torch and the river is too risky to cross without the tourch. if all people cross simultanoesly then torch light wont be sufficient.Speed of each person of crossing the river is different.cross time for each person is 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the river ?

#12 - Fun Math Puzzle

Baseball bat and ball cost $50. If the bat cost $49 more than the ball, what is the cost of each

#13 - Logic Interview Question

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its color and put it back into the box, without seeing the color of the other ball.

How many such operations are necessary to correctly label the boxes?

#14 - Logic Thinking Puzzle

At a restaurant downtown, Mr. Red, Mr. Blue, and Mr. White meet for lunch. Under their coats they are wearing either a red, blue, or white shirt.Mr. Blue says, 'Hey, did you notice we are all wearing different colored shirts from our names?' The man wearing the white shirt says, 'Wow, Mr. Blue, that's right!'
Can you tell who is wearing what color shirt?

#15 - Monty Hall Problem Puzzle

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

#16 - No Uninvited Guest Puzzle

Queen Elizabeth organized a royal party.

To Avoid uninvited guest royal family set a password.
Wayne (an uninvited person) plan to enter the party. He stand nearby the door.

First guest comes, the security person said 'twelve' and guest replied with six.
Second guest comes , the security person said 'six' and guest replied with 'three'.

Wayne thought is enough and he walked to the entry point. The security person said 'eight' , Wayne replied smilingly 'four'.
He was immediately thrown out of the party.

why ?

#17 - Popular Liar Truth Riddle

Suarez is a strange liar.

He lies on six days of the week, but on the seventh day he always tells the truth.

He made the following statements on three successive days:

Day 1: "I lie on Monday and Tuesday."
Day 2: "Today, it"s Thursday, Saturday, or Sunday."
Day 3: "I lie on Wednesday and Friday."

On which day does Suarez tell the truth?

#18 - Most Famous Maths Puzzle

I can prove why 1 = 2

* Lets say y = x
* Multiply through by x xy = x2
* Subtract y2 from each side xy - y2 = x2 - y2
* Factor each side y(x-y) = (x+y)(x-y)
* Divide both sides by (x-y) y = x+y
* Divide both sides by y y/y = x/y + y/y
* And so... 1 = x/y + 1
* Since x=y, x/y = 1 1 = 1 + 1
* And so... 1 = 2

How is this possible ?

#19 - Prison Break Riddle

Two prisoners 'Lincoln Burrows' and 'Michael Scofield' are locked in a cell.
There is open window approx 30 feet above the ground of the cell.
They are never able to reach there.

Then they plan to escape by a tunnel and they start digging out.
After digging for more than 20 days, Scofield comes with the different plan and they escaped.

what was the plan ?

#20 - Classic Logical Interview Puzzle

I have two rectangular wires.
Both of them have property that when i light the fire from one end , it will take 60 minutes to get completely burn.
However they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could i measure 45 minutes ?