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Six X 's have to be placed in the square...

Six X 's have to be placed in the squares of the figure below, such that each row contains atleast one X. in how many different ways can this be done?

Text Solution

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In the given figure there are 8 squares and we have to place 6X's this can be donne in
`.^(8)C_(6)=.^(8)C_(2)=(8*7)/(1*2)=28` ways
But these include the possibility that either headed row or lowest row may not have any X. these two possibilities are to be excluded.
`therefore` Required number of ways=28-2=26
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