MathRevolution
How many possible 6-digit code numbers can be formed from three a, two b, and one c?
A. 40
B. 50
C. 60
D. 70
E. 80
----------ASIDE-----------------------
When we want to arrange a group of items in which some of the items are identical, we can use something called the MISSISSIPPI rule. It goes like this:
If there are n objects where A of them are alike, another B of them are alike, another C of them are alike, and so on, then the total number of possible arrangements = n!/[(A!)(B!)(C!)....] So, for example, we can calculate the number of arrangements of the letters in MISSISSIPPI as follows:
There are
11 letters in total
There are
4 identical I's
There are
4 identical S's
There are
2 identical P's
So, the total number of possible arrangements =
11!/[(
4!)(
4!)(
2!)]
------NOW ONTO THE QUESTION----------
We want to arrange AAABBC
There are
6 letters in total
There are
3 identical A's
There are
2 identical B's
So, the total number of possible arrangements =
6!/[(
3!)(
2!)]
= 60
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