Problema Solution
For a boy having 6 friends, how many ways are there to invite 1 or more of them to the lunch?
Answer provided by our tutors
Ways to invite 1 of them for lunch = 6
Ways to invite 2 of them for lunch = 6C2 = 6!/(4!2!) = 6*5/2 = 15
Ways to invite 3 of them for lunch = 6C3 = 6!(3!3!) = 6*5*4/6 = 20
Ways to invite 4 of them for lunch = 6C4 = 6!/(4!2!) = 6*5/2 = 15
Ways to invite 5 of them for lunch = 6C5 = 6!(5!1!) = 6
Ways to invite 6 of them for lunch = 1
Total number of ways = 6 + 15 + 20 + 15+ 6 + 1= 63