In how many ways can seven person be seat in a row of seats if two persons insist on sitting next to each other?

In how many ways can one post 3 letters in 5 post boxes?

In how many ways can 7 boys and 5 girls be arranged in a row so that no two girls come together?

Can two streamlins cross each other?

In how many ways can 5 boys and 3 girls stand in a row such that no two girls are together?

In how many, ways can 5 boys and 5 girls be placed in a circle,so( that no two boys are side by side?

In how many different ways can one invite 3 or more of his 6 friends?

In how many ways can 5 prizes be awarded to 4 boys if each boy is eligible for any number of prizes?

In how many ways can the letters of the words ALGEBRA be arranged in the form of words so that the two A's donot come together?

In how many ways can 10 scrips be arranged, so that the best and the worst do not come together?

In how many ways can the letters of the words PERMUTATIONS words start with P and end with S.