Find the number of ways you can fill a 3 x 3 grid (with 4 corners defined as a, b, c, d), if you
have 3 white marbles and 6 black marbles
Choose one.
A) 9c3  B) 9c2  C) 9c4  D) 8c3  E) 7c3
The area of the grid is = 9.   Now, No. of ways we can arrange 3 white balls in 9 places = 9c3.   and 6 black balls in  (9-3)= 
<gadget id="calculator"> (9-3)</gadget>
<output>6</output>
6 places= 6c6 = 1.   So total = 9c3 * 1 = 9c3.   In another way,   No ways we can arrange 6 black balls in 9 places = 9c6 = 9c3   and no ways 3 white balls in  (9-6)= 
<gadget id="calculator"> (9-6)</gadget>
<output>3</output>
3c3= 1   No. of ways we can arrange 3 white balls and 9 black balls in 3x3 grid is = 9c3*1 = 9c3   9c3NSWER:9c3
<result>A</result>
Find the number of ways you can fill a 3 x 3 grid (with 4 corners defined as a, b, c, d), if you
have 3 white marbles and 6 black marbles