What is the probability of a needle hitting a line on graph paper?

In summary, the conversation discusses the "buffons needle" riddle which involves calculating the chance of a needle hitting a line on a paper with horizontal lines. However, the speaker misremembered the riddle and instead tried to solve the same question with horizontal and vertical lines on graph paper. They calculated the chance of hitting a line to be 3/pi, which is approximately 95%. Both speakers agree on this answer and note that it proves pi>3 and is close to 3. The speaker suggests using a similar method to approximate pi, though it may not converge quickly. They also mention a program they wrote that simulated the needle falling 10000000 times and gave a similar result for pi.
  • #1
daniel_i_l
Gold Member
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In the "buffons needle" riddle you have a paper with horizontal lines in it all 1 unit apart and you drop a needle 1 unit long - you have to calculate the chance that the needle will hit a line. but i remembered the riddle wrong so instead i tried to solve the same question with both horizontal and vertical lines (graph paper). all of the cells are 1X1 unit. i got that the chance of hitting a line is:
3/pi which is about 95%
is that right?
Thanks.
 
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  • #2
I get the same answer. Also, note the result proves pi>3, and since it's obviously pretty likely the needle will hit a line, it shows pi is pretty close to 3. Maybe you can get other approximations for pi using a similar method, which is ironic considering the point of the original problem was to empirically approximate pi.
 
Last edited:
  • #3
I wrote a program that simulates a needle falling 10000000 times and counts the times that it hits a line. using that i got that
3/pi = 0.95521 or pi = 3.14067 - ok but i guess that this method of calculating pi doesn't converge very fast.
 

Related to What is the probability of a needle hitting a line on graph paper?

1. What is Buffon's needle variation?

Buffon's needle variation is a mathematical problem that involves randomly dropping a needle onto a lined surface and calculating the probability of the needle crossing one of the lines.

2. Who is Buffon and what is the significance of this problem?

Georges-Louis Leclerc, Comte de Buffon, was a renowned French mathematician and naturalist who first proposed this problem in the 18th century. This problem is significant because it has real-world applications in calculating probabilities and has been used to demonstrate the concept of Monte Carlo methods in statistics.

3. How is this problem related to the famous "Buffon's needle" problem?

The original "Buffon's needle" problem involved calculating the probability of a needle crossing a set of parallel lines on a flat surface. Buffon's needle variation is an extension of this problem, where the lines are no longer parallel and can have different distances between them.

4. What is the formula used to calculate the probability in Buffon's needle variation?

The formula used to calculate the probability in Buffon's needle variation is P = 2L/πd, where L is the length of the needle and d is the distance between the lines.

5. Are there any real-world applications of Buffon's needle variation?

Yes, this problem has been used in various fields such as physics, statistics, and computer science to simulate and calculate probabilities in a wide range of scenarios. It has also been used to demonstrate the concept of random sampling and its applications in real-world situations.

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