Thursday, July 29, 2010

Finding height of a room having a hanging bulb

How would you find the height of room if after entering the room with a stop-watch you find there is a hanging bulb that just grazes your head ?

You can apply knowledge of physics here. Just oscillate the hanging bulb. Measure the time period for one complete. Since this would be a Simple Harmonic Motion, you can use the formula T=2 * 3.14 * (L/G)^1/2.
Thus, L will be the length of the hanging thread.
Now you can add your height to L , to find the height of the room.

Draw four equidistant points

How it is possible to place four points that are equidistance from each other?

Only 3 points can be equidistant from each other. But if u place points in the
shape of a pyramid then its possible

Measure time with lighted candles

You are given two candles of equal size, which can burn 1 hour each. You have
to measure 90 minutes with these candles. (There is no scale or clock). Also you have a lighter.

First light up the two ends of the 1st candle. When it will burn out light up
one end of the second candle. (30+60=90)

Classic mathematics puzzle of where two rupees went from Three Friends

There were 3 friends. Each had 20 rupees and agreed to contribute and party at a local restaurant. When they finished their burgers, the waiter gave them a bill of 60 rupees. They readily contributed and paid of the bills by paying 20 each.

A minute later the manager of restaurant announced that there was additional discount on their bill. He gave 10 rupees back to the waiter to return it to boys.

On his way towards the group, the greedy waiter put 2 rupees with himself and also gave another 2 rupees to one of his companion. He distributed remaining 6 rupees between three boys by tendering 2 rupees to each of them.

The boys felt happier as the burger now costed them 18 rupees each (20-2).

The problem comes as follows:
Each boy initially gave=20
Each received=2
Therefore, each spent = 20-2=18
Now, total spent=18*3=54
2 rupees with waiter number 1 ie. 54+2=56 rupees
2 rupees with waiter number 2 ie. 56+2=58 rupees
And this turns out to be a problem.
We should finally amount to 60 rupees. But what we calculate is just 58 rupees. so, where is the additional 2 rupees gone??

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