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 
Option: C Explanation : Click on Discuss to view users comments. 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!(6n!)) 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

The number of ways to arrange th a letters of the word CHEESE are
A.  120 
B.  240 
C.  720 
D.  6 
Option: A Explanation : Click on Discuss to view users comments. Sreenivasulu.G said: (2:49am on Friday 7th April 2017)
6!/3! = 6×5×4 = 120

The number of different permutations of the word BANANA is
A.  720 
B.  60 
C.  120 
D.  360 
Option: B Explanation : Click on Discuss to view users comments. Govendhan said: (11:31pm on Tuesday 19th December 2017)
6!/(3!*2!)=60

The number n of ways that an organization consisting of twenty six members can elect a president, treasurer, and secretary (assuming no person is elected to more than one position) is
A.  15600 
B.  15400 
C.  15200 
D.  15000 
Option: A Explanation : Click on Discuss to view users comments. 
Common Data for next 2 questions
There are four bus lines between A and B; and three bus lines between B and C.
The number of ways a person can travel by bus from A to C by way of B will be
A.  10 
B.  12 
C.  14 
D.  24 
Option: B Explanation :
There are four ways to go from A to B and three ways to go from B to C. Click on Discuss to view users comments. 