InterviewSolution
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InterviewSolution
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A man has three friends. The number of ways he caninvite one friend everyday for dinner on six successive nights so that no friend is invited morethan three times isa. `640`b. `320`c. `420`d. `510`A. 360B. 420C. 170D. 510 |
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Answer» Correct Answer - D Let x,y,z be the friends and a,b,c denote the case when x is invited a times, y is invited b times and z is invited c times. Now, we have the following possibilities (a,b,c)=(1,2,3) or (2,2,2) or (3,3,0) Hence, the total number of ways `=(6!)/(1!2!3!)xx3!+(6!)/(2!2!2!)xx(3!)/(3!)+(6!)/(3!3!0!)xx(3!)/(2!)` `=360+90+60=510` |
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