I have two problems and I don't know how to solve them.

1) if you have a triangle of circles with 1 circle at the top with two circles below that, three circles below that etc. How would you find the the number of circles in the 90th row ? Or which row would contain 90 circles. I think there would be a formula, or uses Combinations/Permutations to solve the problem.


2) how do you find distance on a grid map where the points are not exactly on the grid line:
Point A .


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- (this is a bridge)
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. Point B


Point A would be on the graph line, you have to cross the Bridge and point B is not on the grid line.

3) Trail L/R problem- How do you figure the quickest way from point A to point B if the trail splits L or R 6 times?

Any help would be appreciated. Thanks RH