what is the probability?

Question

if a needle is dropped on parallel grid lines whisch are spread 2 needle lengths apart what is the probability that ht eneedle will cross a grid line?

Answer 1

This is called the Buffon needle problem.

In general the probability is 2l/(tπ). l is the needle length, t is the spacing. If t=2l then the probability is 2l/(2lπ) or P=1/π, From this example, you could estimate the value of π although this would take you many trials.