Question

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

Answer 1

$5⟶$ Flags

Each signal needs two glags

Therefore number of possible signals

${\Rightarrow }^5{P}_2\Rightarrow \frac{5!}{3!}\Rightarrow 5\times 4\Rightarrow 20$

Hence the correct answer is $20$ signals