Question

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

Answer 1

Given, $5$ flags of different colours
Finding number of signals from $2$ flags.
A signal can have only $2$ flags.
Number of different ways for position of first flag $=5$
Number of different ways for position of first flag $=4$

$\therefore$ Required number of Signals $=5\times 4=20$