The problem is

A jar contains 6 red balls, 3 green balls, 5 white balls and 7 yellow balls. Two balls are chosen from the jar, with replacement. What is the probability that you choose a red and a yellow ball?

I know that they do not affect each other so could be independent events, so P(red and yellow) = P(red) x P(yellow) so 6/21 x 1/3 = 2/21

However, I do not know why my tree diagram isn't working

----6/21---- Red----7/21---- Yellow---6/21--- Red

---7/21---Yellow

---3/21---Green

---5/21---White----3/21---- Green---6/21--- Red

---7/21---Yellow

---3/21---Green

---5/21---White----5/21---- White---6/21--- Red

---7/21---Yellow

---3/21---Green

---5/21---WhiteI've been taught you multiply across for the probability.---6/21--- Red

---7/21---Yellow

---3/21---Green

---5/21---White

I get two values for the probability.

P(yellow and red)=2/21

P(red and yellow)=2/21

Do you not add these two together to get 4/21?

I'm really confused now as to which one is correct.