In a 3x3 grid, point A is on the last row (at the 1st corner), point X is on the middle row (between box 1 and 2) and point B is on the top row (at the upper corner of the last box). A path from point A to point B is determined by moving upward or to the right along the grid lines. How many different paths can be drawn from A to B that DOES NOT include X?
The answer is 8, but how would I get that?
The answer is 8, but how would I get that?
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First from A to B, there are 20 （6C3=6x5x4/(1x2x3)=20) paths in total.
then, the paths including X are 12(2C1x4C2=2x6=12)
∴the paths that doesn't include X are 8(20-12=8）
so the answer is 8
you're right :-)
then, the paths including X are 12(2C1x4C2=2x6=12)
∴the paths that doesn't include X are 8(20-12=8）
so the answer is 8
you're right :-)
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Not really easy for me.