A disk that is 1 cm in diameter is tossed onto a 6x6 grid of squares with each square having side length 1.25 cm.
A disk is in a winning position if no part of it touches or crosses a grid line otherwise it is in a losing position
The disk is tossed and it lands in a random position so that no part of it is outside the grid.
What is the probability that the disk is in a winning position?
The grid is 7.5x7.5 cm and the center of the disk cannot be within .5 cm of the edge of the grid and so is limited to a 6.5x6.5 area.
There are 16 central 1.25x 1.25 squares, in which there is a .25x.25 area in which the tossed disk's center can fall and win. In fact each of the 36 squares of the grid contains this .25x.25 possible area for a win. The winning area of the board is 2.25 cm^2.
2.25/(6.5*6.5) = 2.25/42.25 = 9/169 ~= 0 .0532544378698225
is the probability of not falling on a line given that it has fallen completely within the grid.
Correcting original post where I had 36*.25^2 equalling 6.25; looks like I had multiplied by 100 instead of 36.
Edited on July 8, 2016, 8:51 pm

Posted by Charlie
on 20160708 11:17:15 