1thnks avik.
u deserve a pink post.
A bag contains 4 white balls and 5 black balls : a second bag contains 3 white and 4 black balls: and a third has 5 white and 4 black balls.
A ball is randomly picked from the first bag and put in the second: then another ball is picked from at random from the second bag at put in
the third. If now a ball is randomly picked from the third bag, wat is the probability that it is white ?
ans---->391/720
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2 Answers
13Favourable Cases -
Ball picked...
→ White frm I, White frm II, White frm III
= 4/9*4/8*6/10 = 96/720
→ White frm I, Black frm II, White frm III
= 4/9*4/8*5/10 = 80/720
→ Black frm I, White frm II, White frm III
= 5/9*3/8*6/10 = 90/720
→ Black frm I, Black II, White frm III
= 5/9*5/8*5/10 = 125/720
Summing up all, we'll get - P(white frm III) = 391/720.