00:01
There are four classes, each with a president, vice president, and secretary treasurer.
00:09
An all -school council with four officers is to be formed from these representatives.
00:17
So in how many ways can you choose four officers from these representatives? so since each class has a president and there are four classes, then there would, be four presidents among the representatives.
00:37
Similarly, there would be four vice presidents and four secretary treasurers.
00:43
So for that question, you want to choose four officers from 12 representatives, four plus four plus four.
00:54
So that can be done in combination 12 taken four number of ways.
01:04
Now, if you have a calculator that could calculate combinations directly, then you can use that.
01:11
Otherwise, you'll need the combination rule, right, which basically says that combination n taken r is equal to n factorial over n minus r factorial times r factorial.
01:26
Which means this would be equal to 12 factorial over 8 factorial times 4 factorial.
01:35
Then you could use your calculator...