To determine the variance of X, we must first determine the variance of Y.
Expected value E(Y)=sumytimesP(y)=(0times0.3)+(1times0.2)+(2times0.4)+(3times0.1)=0+0.2+0.8+0.3=1.3
Expected value of Y2, E(Y2)=sumy2timesP(y)=(02times0.3)+(12times0.2)+(22times0.4)+(32times0.1)=0+0.2+1.6+0.9=2.7
Variance Var(Y)=E(Y2)−[E(Y)]2=2.7−(1.3)2=2.7−1.69=1.01
Given X=2Y+10:
According to the properties of variance, Var(aY+b)=a2timesVar(Y).
Var(X)=22timesVar(Y)=4times1.01=4.04.
The closest option given is 4.