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Lattice paths through at least one of two bonuses

Question

On a grid you start at (0,0)(0,0) and must reach (6,6)(6,6) using unit moves to the right or upward only. Bonus items sit at the points (2,3)(2,3) and (4,6)(4,6). How many such paths pass through at least one bonus point?

Short answer

460460. Use inclusion–exclusion. Through (2,3)(2,3): (52)(74)=350\binom52\binom74=350. Through (4,6)(4,6): (104)⋅1=210\binom{10}{4}\cdot1=210. Through both: (52)(52)⋅1=100\binom52\binom52\cdot1=100. Total 350+210−100=460350+210-100=460.

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