Ramesh has 6 friends. In how many ways can he invite one or more of them at a dinner ?
| A. | 61 |
| B. | 62 |
| C. | 63 |
| D. | 64 |
Answer : C Explanation : Aditya said: (1:24am on Tuesday 29th January 2013)
You seem to be looking for Sum[C[6,n], n=1..6], where C[6,n] = 6!/(n!(6-n!)) is the number of combinations of 6 things taken n at a time.c[6,1]=6!/(1!5!)=6c[6,2]=6!/(2!4!)=15c[6,3]=6!/(3!3!)=20c[6,4]=6!/(4!2!)=15c[6,5]=6!/(5!1!)=6c[6,6]=6!/(6!0!)=1sum[6,15,20,15,6,1]=63
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Option: A Explanation : Explanation will come here. Explanation will come here. Explanation will come here. Explanation will come here. Explanation will come here. |
