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**Knew43****Member**- Registered: 2022-11-15
- Posts: 1

> Hi,

>

> I have a question that you maybe able to help me with.

>

> I to get all the combinations for this problem. I have 3 different categories. I have 5 objects for in each category. So a total of 15 objects. How do I get the total number of combinations. So that means that that there will be a object from each three of the categories.

>

> I could find an example on the combinations page!

>

So I need a manager from each on of these three buckets;

Engineering- A,B,C,D,E,F Data architect-G,H,I,J,K,L. DevOps- M,N,O,P,Q,R

Now I need all the combinations that can be. ONLY 1 can come from each bucket. For example one combo is A,G,M.

Im not sure how to use the calculator on the website to enter the above condition.

Please help if you can.

Ken

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**Bob****Administrator**- Registered: 2010-06-20
- Posts: 9,607

hi Knew43,

Welcome to the forum.

If you had one set {A,B,C,D,E} and you had to choose any 3 this would be a combinations problem.

{5x4x3)/(3x2x1)

If you had to choose them and order matters (so that ABC and BCA are different) then the problem becomes a permutions one. 5x4x3

Where do these calculations come from. Let's deal with the permutations first.

There are 5 choices for the first selection; then 4 choices then 3. This gives 5x4x3 altogther.

If it doesn't matter which order we select them, for example, ABC, ACB, BAC, BCA, CAB and CBA have all been counted so divide by 3x2x1 to get the number of combinations.

For your problem we are making 3 independent selections; so deal with each separately and then times them together.

So choose one from {A,B,C,D,E,F} That's 6C1 ie 6.

Same for the next two selections so the number of ways to make these three selections is 6 x 6 x 6.

If each set has only 5 members then do a similar calculation with 5s.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob

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**Zazu****Member**- Registered: 2022-11-22
- Posts: 3

Hi i did not know how to create a post here so i replied to this post. My question is how do we calculate negative minus negative because everytime i fail exams because of the negative numbers

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**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 40,492

Hi Zazu,

I think this link How to Add and Subtract Positive and Negative Numbers my be helpful.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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