Wednesday

October 1, 2014

October 1, 2014

Posted by **doug** on Monday, March 14, 2011 at 8:12pm.

- math -
**MathMate**, Tuesday, March 15, 2011 at 10:15amThe number of ways is denoted (18,4), pronounced as "18 choose 4".

Basically, we would choose the first one from 18, second from 17,....

Since the choices are independent, the number of choices are multiplied together to get 18*17*16*15.

However, since the order of choices is not important, we have over-counted by 4*3*2*1 times, so the result should be divided by this factor, so

(18,4)=18*17*16*15/(1*2*3*4)

=(18!/14!)/4!

=18!/(14!4!)

where 18! means factorial 18.

In the general case,

(m,k)=m!/((m-k)!k!)

**Answer this Question**

**Related Questions**

statistic - here are five seniors in a class, for each situation, write how the ...

math logic - A group of five students needs to break into two smaller groups in ...

management - Think of a recently completed group project that you have been ...

History - My teacher wants us to do a project on the 90's. In my group, I was ...

management - Think of a recently completed group project that you have been ...

project Manangement - Think of a recently completed group project that you have...

Math - Ok, so my math teacher didn't tell us ways to do this faster, and it's ...

Child Care - You overhear a group of children saying, "Girls can't be truck ...

math - In English Class, after studying a book called \The Lord of the Flies" by...

math - Simon must choose one fiction book and one biography for a reading ...