Four students need to be selected from a class

of 15 to help clean up the campus. How many different ways can the 4 students be chosen?

Find the number of words, with or without meaning, that can be formed with the letters of the word ‘CHAIR’.

How many ways can a club select a president, vice president, and a secretary from a group of 5 people?

In Cornville, bicycle license plates have 2 letters followed by a 1-digit number. How many different license plates are possible?

When three-digit telephone area codes were first put in place, the first number could be any digit (2-9), the second number could only be 0 or 1, and the third could be any digit (0-9). How many possible area codes can be created with this format?

A DJ has to choose three songs for the last few minutes of his evening show. If there are nine songs that he feels are appropriate for that time slot, then how many ways can he choose and arrange to play three of those nine songs?

There are 15 racers running a race. There are medals for the first three racers to cross the finish line. How many ways are there to award medals to the first three racers?

A combination lock has 7 digits. How many distinct combinations does this lock have if the numbers used have to be 0 through 5? (time:2mins)

There are 12 persons in a party and if each two of them shake hands with each other ,How many handshakes happen in a party

A convex polygon has 44 diagonals. Find the number of its sides.

In how many ways can a football team of 11 players be selected from 16 players? How many of them will include 2 particular players?

If nC12 = nC8, then n is equal to