Give 5 flags of different colours, how many different-signal can be generated. If each signal requires the use of 2 flags one below the other.

A Signal is generated from 2 flags by putting one flag above the other. If 4 flags of different colours are available, how many different signals can be genereted?

How many different words are formed if the letters R is used thrice and letters S and T are used twice each?

A committee of 6 is to be chosen from 10 men and 7 women, so as to contain at least 3 men and 2 women. In how many different ways can this be done, if two particular women refuse to serve on the same committee?

How many even numbers can be formed by using all the digits 2, 3, 4, 5, 6?