# probability problem..pls help

• Oct 16th 2012, 09:03 AM
abhay11150
probability problem..pls help
there are 2 persons A and B. they decide to meet in a park between 10 am to 11 am. it was decided that whosoever comes first will wait for the other person for exactly 20 minutes. what is the probability that they do not meet? Please provide multiple methods of solving. Thanks.
• Oct 16th 2012, 09:15 AM
richard1234
Re: probability problem..pls help
This is a fairly classic problem...one of the solutions involves drawing a square of side length 1 on an xy-plane (say, with coordinates (0,0), (1,0), (1,1), (0,1)). We label the axes so that the x-axis corresponds to A's arrival time, and the y-axis corresponds to B's arrival time. Here, (0,0) corresponds to both A and B arriving at 10:00, (1/2, 1/2) corresponds to both A and B arriving at 10:30, and so on.

The probability that A and B do meet is given by a certain geometric region S. Find the area of S. The probability that they do not meet is simply 1-S.