There are 3 red and 7 black marbles in a bag. If I am blindfolded, how many times must I reach in and pull out a marble before I am sure it is a black one?

• 4times.
  there are 3 red and 7 black marbles..
  even if the person picks up 3 marbles(all of them may be red or may be not).
  so the next marble wud be black in 1st case and if not black then also the person has has drawn the black one earlier
• 10 years agoHelpfull: Yes(0) No(0)