Posted by **rishabh** on Monday, June 10, 2013 at 10:54pm.

Consider a 25×25 grid of city streets. Let S be the points of intersection of the streets, and let P be the set of paths from the bottom left corner to the top right corner of which consist of only walking to the right and up. A point s is chosen uniformly at random from S and then a path p is chosen uniformly at random from P. Over all (s,p) pairs, the probability that the point s is contained in the path p can be expressed as ab where a and b are coprime positive integers. What is the value of a+b?

Details and assumptions

There are 25 streets running in each direction, so S consists of 625 intersections.

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**ok**, Wednesday, June 12, 2013 at 11:16am
where did you get this question?

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**Anonymous**, Wednesday, June 12, 2013 at 2:45pm
It comes from an Olympiad Maths problem

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**ok**, Wednesday, June 12, 2013 at 5:18pm
Can I have a link please?

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**Anonymous**, Thursday, June 13, 2013 at 6:11am
It does not have a link.

It is on paper.

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**ok**, Thursday, June 13, 2013 at 8:06am
Ok.

These are lame cheaters.

DO not provide them answers.

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**ok**, Thursday, June 13, 2013 at 11:20am
SOlved.

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**not OK**, Thursday, June 13, 2013 at 9:58pm
to ok. if you want to answer this on the site brilliant, you can by making an account but unfortunately, in every account, they have different sets of question basing on the level what you are in. this is such a very easy question.

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**ok**, Friday, June 14, 2013 at 6:39am
Share your link, as I cannot create an account.

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**ok**, Friday, June 14, 2013 at 3:23pm
Well my answer is 49/625

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