10 pencils and 8 pens are in a box, 11 writing utensils are to be selected at random, without replacement from the box, If the pens and pencils are equally likely to be selected, determine the probability that seven pencils and four pens are selected.

Question

anonymous · Answer

I think it is 10 Choose 7 times 8 Choose 4

10!             8!
----   *    ----
7! 3!          4!4!

anonymous · Answer

{(10C7)*(8C4)]/(18C11)

anonymous · Answer

10 * 9 * 8 * 7!
------------  =  120
7! * 3 * 2 * 1


8 * 7 * 6 * 5 * 4!
-------------- = 70
4! * 4 * 3 * 2 * 1

anonymous · Answer

18!
----
11! 7!

18 * 17 * 16 * 15 * 14 * 13 * 12 *11!
--------------------------------- = 31824
11! * 7 * 6 * 5 * 4 * 3 * 2 * 1

anonymous · Answer

120 * 70
--------
31824



8400
------  needs to be reduced.
31824

anonymous · Answer

175/663