P (one white ball & one black ball ) P {[black from 1 st bag & white from 2nd] or [white from 1 st & black from 2nd]} =P([B1∩W2)∪(W1∩B2)] =P(B1∩W2)+P(W1∩B2) (By addition theorem for mutually exclusive events) =P(B1)P(W2)+P(W1)P(B2) (∴B2 & W2;B2 & W1are pairs of independent events) =[