Sunday, March 23, 2008

Rank the 25 horses puzzle

Rank the 25 horses puzzle

You are given 25 horses, you need to rank them on the basis of their speed. They all run at the same speed everytime. Given that you can run only 5 of them at a time.

1: What do you think how many races to will it take to rank all of them from 1 to 25
2: how many races will it take to find out the fastest one?
3: how many races will it take find the top 5 fastest?


Thursday, March 20, 2008

Coins In A Row Puzzle Solution

This is the solution to the Coins in a row riddle posted on 10th Feb 2008. Before going forward try the puzzle at Coins in a row puzzle.

It turns out that we can answer this puzzle by starting with a simple 2 by 2 checkerboard, with a head in the lower left corner. This board obviously has 1 coin of one type, and three of the other.

We have four allowed moves. Flipping row 2 or column 1 leaves us with 1 head and 3 tails, but we prefer to think of this as 1 coin of 1 type, and 3 of the other. Flipping row 1 or column 2 changes two tails to heads, but still leaves us with 1 coin of one type, and 3 of the other.

In other words, every move we make leaves 1 of one kind and 3 of the other. So we can never use these moves to get a board that is all the same type.

If we can assume that our checkerboard has at least 2 rows and 2 columns, then the analysis for the 2 by 2 board above still applies. In other words, given, for example, a 6 by 17 board, we simply note where the one head is, and look at the little 2 by 2 square containing that head and three tails. Although lots will happen all over the board as we make moves, we concentrate on this one little area. Just as before, the little area will always have 1 coin of one type and 3 of the other. Therefore, the board can never be all of one type.


This analysis will not apply if the board has only one row, or only one column, but of course, then it's obvious that the coins can all be matched.

It should also be obvious that the actual location of the single head doesn't matter.

Wednesday, March 5, 2008

Great Grandpa bridge puzzle

Great Grandpa Bridge Puzzle
Here’s a puzzle my great grand-daddy told me in my Dreams. "son, when i was civil engineer there was once A great embarrassment.
Once across two points in the City there was a huge traffic of people but no Direct road. They had to travel great lengths in order to reach Their destination.the governor ordered me to build a road across those two points. It was completed in five years. But Horrors of horrors, as soon asteroid was built, it was No longer required!
The very construction of the road had rendered it useless and unessential. And for that the new governor castigated me and tarnished my good name. So much so that my spirit still lingers in these Parts.
Oh if someone could tell me a reason for my Undoing, i might rest in peace."

Monday, March 3, 2008

Solution to the Birbal the Wise Puzzle

This is the solution to the puzzle Birbal the Wise Puzzle posted on 24th January 2008. Before reading on , please try the puzzle at Birbal the Wise Riddle, if you havent tried it as yet. Its worth trying!!!
Birbal stated that there weren't any barbers in heaven and said that was the reason for his long beard. Since Akbar now knew a way to reach them, he asked for his barber to be sent. Realizing that he would die in the fire, the emperor's barber confessed what he and the ministers did and no one dared to conspire against Birbal again.

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