yesterday question ........
.. Find the number of ways you can fill a 3x3 grid (with 4 corners defined as a,b,c,d) if you have 3 white marbles and 6 black marbles...

.....A. 9 C 3

....B. 6 C 3

.......C. 9 C 3 + 6 C 3

.....D. (9 C 3) + (6 C 3)/3!

• ans is 9c3
• 10 years agoHelpfull: Yes(5) No(0)
• 9!/(3!*6!)=9C3....u can arrange all 9 marbles in 9! ways ...but, since 3 white marbles are the same and 6 black ones...therefore..divide 9! by 3!*6!...hence ans=9!/(3!*6!). B) is correct
• 10 years agoHelpfull: Yes(3) No(4)
• we have to fill it with 3 white and 6 black marbles.so,
  case i-using white first then no. of ways=9C3 * 6C6=9C3
  case ii-using black first then no. of ways=9C6 * 3C3=9C6=9C3
  Ans-9C3+9C3=2 * 9C3=2 * 9C6
• 10 years agoHelpfull: Yes(0) No(2)
• dice having prime no. ...and roll 10 time ...do you remember the questions and answer ??
• 10 years agoHelpfull: Yes(0) No(0)