Let event J_{1} : Ball drawn from jar I,

event J_{2} : Ball drawn from jar II.

P(J_{1}) = P(head) = 1/2

P(J_{2}) = P(tail) = 1/2

Let event W: Ball drawn is white.

In Jar I, there are total 12 balls, out of which 5 balls are white.

∴ Probability that the ball drawn is white under the condition that it is drawn from Jar I.

P(W/J_{1}) = \(\frac {^5C_1}{^{12}C_1} = \frac {5} {12}\)

Similarly, P(W/J_{2}) = \(\frac {^3C_1}{^{15}C_1} = \frac {3} {15} = \frac 1 5\)

Required probability = P(J_{2}/W)

By Bayes’ theorem