A box contains 40 numbered red balls and 60 numbered black balls. From the box, balls are drawn one by one at random without replacement till all the balls are drawn. The probability the that last ball drawn is black equals to
a) $1/100\quad $ b) $1/60\quad $ c) $3/5\quad $ d) $2/3\quad $
total red balls=40 ,
total black balls=60
The probability of drawing last black ball=total black balls/(total balls)
I guessed this answer which is correct but i don't think that my procedure is correct. I think there should be a correct solution to such problems of probability. Please give correct solution to this problem.
My book suggests that answer must be 3/5