A jar contains 3 nickels and 2 dimes. You reach in and randomly select 2 coins. Let x represent the value of the two coins in cents. Find the expected value and standard deviation of x

Answer 1

Let
N=event of picking a nickel (5 cents)
D=event of picking a dime (10 cents)
X()=value of outcome
P()=probability of outcome
Possible outcomes:
NN : X(NN) = 10 P(NN)=(3/5)(2/4)=3/10
ND : X(ND) = 15 P(ND)=(3/5)(2/4)=3/10
DN : X(DN) = 15 P(DN)=(2/5)(3/4)=3/10
DD : X(DD) = 20 P(DD)=(2/5)(1/4)=1/10

E[X]=Σ X(k) P(k) where k=all possible outcomes.
E[X²]=Σ X(k)^2 P(k)
σ²=E[X²]-(E[X])²
Standard deviation = √(σ²)

Answer 2

i have no clue