# Math Help - Mean of a tree diagram

1. ## Mean of a tree diagram

What is the equation for finding E(S2)

Thanks

2. ## Re: Mean of a tree diagram

$E(S_2)=1\cdot \mathcal{P}(1)+6\cdot \mathcal{P}(6)+9\cdot \mathcal{P}(9)$

3. ## Re: Mean of a tree diagram

Originally Posted by Plato
$E(S_2)=1\cdot \mathcal{P}(1)+6\cdot \mathcal{P}(6)+9\cdot \mathcal{P}(9)$
Is P(1) just 1/5 x 2/3???