Riddle:

The figure below is a map of part of a city: the small rectangles are blocks and the spaces in between are streets. Each morning a student walks from intersection A to intersection B, always walking along the streets shown, always going east or south. For variety, at each intersection where he has a choice, he chooses with probability 1/2 (independent of all other choices) whether to go east or south.

Find the probability that, on any given morning, he walks through intersection C

Python Solution:

Riddle Source:

https://artofproblemsolving.com/wiki/index.php/1982_AHSME_Problems/Problem_25