If you have to finish with a double in a game of darts, which number has the most number of different ways of finishing with 2 darts? (for instance 20 could be 18 and double 1, double 8 and double 2, treble 2 and double 7 etc )
Suppose 4 digits 2 ,4,6 and 9 are given. You have to make a four-digit number. In how many ways it can be done, if repetition of the numbers does not allowed?
A double Decker bus can accommodate 80 passengers 35 in upper deck and 40 in lower deck. In how many ways can a group of 80 passengers be accommodated if 5 refuse to sit in the lower deck and 10 refuse to sit in the upper deck
