Question

Consider the two random experiments. Tossing a fair coin once

Answer 1

Tossing a coin $\left(S\right)=\{H,T\}\therefore n\left(S\right)=2$
Elementary events are, $E_1=\left\{H\right\},E_2=\left\{T\right\}\therefore P\left(E_1\right)=\frac{1}{2}P\left(E_2\right)=\frac{1}{2}$
By adding $P\left(E_1\right)$ and $P\left(E_2\right)$, we get
$P\left(E_1\right)+P\left(E_2\right)=\frac{1}{2}+\frac{1}{2}=1$