I thought this is a real cool problem… IT is all about logical thinking…

A teacher took out 8 stamps from a box – four of them white and four of them black. He got three of his brightest students – X, Y and Z and made them stand facing each other. He showed them the stamps, blindfolded each of them and then put two stamps on each of their foreheads. He put the final two stamps back in the box and closed the box. Then he opened the blindfolds. So, each of X, Y and Z could see the stamps on the forehead of the other two (but not their own – or the ones in the box). But they could obviously hear each other.

The teacher asked X first what were the color of the stamps (White White or Black Black or White Black) on his forehead. He said he did not know. The teacher asked then Y the same question. Y said he did not know either. Similarly the teacher asked Z and he too replied he did not know.

The teacher went back to X and asked if he now knew what he had. X again replied in the negative. The teacher asked Y next. And he did answer.

What was his answer? How did he deduce it?

Try this one. It is not as simple as it might sound but not as complicated either.

You have six identical balls except two are painted red, two are painted blue and two are painted white. You know one ball of each color weighs 10 pounds and one ball of each color weighs 11 pounds. (So each color has one lighter ball and one heavier ball).

You have a scale and pan balance but no weights. Only the balance and the six balls.

What is the minimum number of weighings you have to do to determine which are the heavier balls and which are the lighter balls?

I came up with this puzzle on my flight this evening. Therefore, my solution is not fully vetted. I will put my solution and then hopefully some of you will either show a better solution or vouch for mine. As of now, I am going to post the puzZle and hit the sack. I will check your answers tomorrow.

You have a traditional weighing scale and pan balance – you know where you can put weights or stuff on any of the two sides… You also have the following weights (don’t worry about the units): 1, 10, 100 and 1000.

The question is – how many different weights can you weigh combining the above weights?

I can’t find the answer to the question I had for myself today. I Googled but still can’t find it. The question is – Which river forms the longest international boundary?

Speaking of rivers and international boundaries, what is your guess about which river crosses the maximum number of international borders? In fact, it flows thru as many as 10 countries.

Here is another interesting trivia question – there is a point close to the above river where three country borders meet. At that point is a picnic table that is shaped as an equilateral triangle! The sides are parallel to the borders! There are three benches on the three sides with the appropriate country’s flag imprinted on their side. You can eat your food and jump from country to country without needing any visa!! Want to guess what those countries are?

I took this grainy picture as I was driving last evening. It was very cloudy and the picture is not the best. But here is a question. There is something unique about the flag that you see. Can you guess what it is?

I will give you two hints – Look at the relative size of the car on the highway. And the other hint is I was in Wisconsin last evening.

This week I was with Arijit and he mentioned that he had not seen me posting puzzles in some time. And that is true. I had not received much answers or attempts for the last few ones. I figured nobody was interested. Let’s see how this one does. This is dedicated to Arijit.

Send me answers as personal messages on FB  instead of comments.

Can you come up with a ten digit number where the first digit is also the count of 1s in the full number, the sound digit is also the count of 2s, the third digit is also the count of 3s and so on and finally the tenth digit is the number of 0s in the number.

Three years and two months back, I had posted a variation of this problem.

There is a box with 99 white balls and 101 black balls in it. And you have a lot of white and black balls outside the box. 

You pick two balls at random from the box. If they are a black and a white, you throw the black ball out and put the white ball back in the box. If however, you got two whites or two blacks then you throw both of them out and instead put back a black one from the pile outside.

Now, you keep doing this till you have one ball left in the box.

What color is the ball?