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Homework Help: Grids and Pascal's Triangle

  1. Apr 22, 2012 #1
    1. The streets of a city are laid out in a rectangular gird, as shown below


    a) Use combinations to find the number of routes through the grid that lead from point A to point B by only travelling north or east. Show your calculations

    b) How many of these routes pass through intersections C

    2. Alright, so I've solved similar questions before. I get to P(66,6)/6! only to get some absurd answer. I understand that from point A to point B there is a distance of 66 blocks-11 east, 6 north. Somehow I believe that the exponential answer that comes from this is not what my professor expects.

    I was wondering if I could have help with this please and thank you :D
    Last edited: Apr 22, 2012
  2. jcsd
  3. Apr 22, 2012 #2
    How did you get 66 blocks? No matter how you travel, the most you could possibly get is 17 (11 east + 6 north). Multiplying gives you the area, not the distance.
  4. Apr 22, 2012 #3
    Whoops, lmao, sorry long day, that makes so much sense, I know what to do from here lol
  5. Apr 22, 2012 #4
    Np, I know the feeling, gl :P
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