Quantum mechanics(expected probability)

[member 141513]

Homework Statement

suppose we have two particles, first with probable states A1,A2,A3 and state B1,B2,B3 each with a certain probability P
Now if we know the probability of composite state |C> is Q
what is the probability to get the first particle to be A1?

im troubled. please help thanks

Here ,probability of getting C is any linear combination of A and B = aP(A)+bP(B)

Homework Equations

The Attempt at a Solution

i have tried to do like this
because C equals one of these 9 states (A1,A2,A3)+(B1,B2,B3)
lets call them |1>,|2>,...,|9>

i don't know how to relate use the "resultant" prbability to get back the original component probability

is it correct to use, for example <C|1> in calculation, I am in trouble

 

[Klockan3]

You have a very fuzzy explanation of the problem, but isn't it as simple as (A1,Bi) summed over i?