Given 7 flags of different colours, how many different signals can be generated if a signal requires the use of two flags, one below the other?

Given 4 flags of different colours,how many different signals can be generated,if a signal requires the use of 2 flags one below the other?

Given 5 flags of different colours,how many different signals can be generated if each signal requires the use of 2 flags,one below the other?

Given 4 flags of different colours,how many different signals can be generated,if a signal requires the use of 2 flags one below the other?

Four flags of different colours are given. How many different signals can be genrated, if a signal requires the use of two flags, one below the other?

How many different signals can be made with 6 given flags of different colours ?

Holme's signals can be given using :

How many different signals can be given using any number of flags from 5 flags of different colors?