# A question in combination

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If we can climb one stair, one stair, or two stairs, two stairs, in what ways can we climb n stairs?

Edited by Strange
Fixed formatting to make text more readable.
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Is it required to yell the question?  Why are you repeating stuff?  When you are yelling stairs do you mean steps instead of stairs?

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12 minutes ago, Bufofrog said:

Is it required to yell the question?  Why are you repeating stuff?  When you are yelling stairs do you mean steps instead of stairs?

Sorry because of the miss understandig.

I meant that to climb stairs one by one or decussate.

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1 hour ago, Vishtasb said:

If we can climb one stair, one stair, or two stairs, two stairs, in what ways can we climb n stairs?

I don't understand the question, but this might help: https://www.mathwords.com/c/combination_formula.htm

1 hour ago, Vishtasb said:

If we can climb one stair, one stair, or two stairs, two stairs, in what ways can we climb n stairs?

I assume the answer is: n stairs, n stairs. But I don't know what it means.

3 minutes ago, Vishtasb said:

I meant that to climb stairs one by one or decussate.

How do you climb stairs in an X-shape?

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10 minutes ago, Strange said:

I don't understand the question, but this might help: https://www.mathwords.com/c/combination_formula.htm

Let me ask the question in other words.

Assume a persion who wants to climbe n stairs. But this persion can only climb stairs one by one or decussate.

There is how many ways that this guy can climb these stairs?

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9 minutes ago, Vishtasb said:

Let me ask the question in other words.

Assume a persion who wants to climbe n stairs. But this persion can only climb stairs one by one or decussate.

There is how many ways that this guy can climb these stairs?

Two ways: one at a time, or two at a time.

Or do you mean, how many ways can you permute 1 and 2 out of the 10 stairs? In which case, I would recommend writing them down. Start with the easy ones:

• 1 1 1 1 1 1 1 1 1 1
• 2 2 2 2 2
• 1 1 1 1 1 1 1 1 2
• 1 1 1 1 1 1 2 2
• and so on

Maybe start with a number less than 10 and see if you can work out the pattern and hence equation.

If that is the question, it is an interesting one. It is bit subtler than the usual combination case, because the total number of "objects" (steps taken) varies.

(And you should look up decussate in a dictionary. I don't think it means what you think it does.)

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9 minutes ago, Strange said:

Two ways: one at a time, or two at a time.

Or do you mean, how many ways can you permute 1 and 2 out of the 10 stairs? In which case, I would recommend writing them down. Start with the easy ones:

• 1 1 1 1 1 1 1 1 1 1
• 2 2 2 2 2
• 1 1 1 1 1 1 1 1 2
• 1 1 1 1 1 1 2 2
• and so on

Maybe start with a number less than 10 and see if you can work out the pattern and hence equation.

And you should look up decussate in a dictionary. I don't think it means what you think it does.

Sorry but It's not my fault.😓

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For the first combination: 1 1 1 1 1 1 1 1 1 1. Just one permutation.

For the first "mixed" combination: 1 1 1 1 1 1 1 1 2. There are 9 possible permutation here (the 2 can be in any position)

Then the next one: 1 1 1 1 1 1 2 2. There are 7 + 6 + 5 + 4 + 3 + 2 + 1 = 28 permutation.

So that is 38 permutations so far. Carry on for all the others ...

20 minutes ago, Vishtasb said:

Sorry but It's not my fault.😓

That is a shame. I often use and recommend Google Translate. It is obviously not perfect!

I think you want to say "in pairs" or "pairwise" or "two at a time".

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10 minutes ago, Strange said:

For the first combination: 1 1 1 1 1 1 1 1 1 1. Just one combination.

For the first "mixed" combination: 1 1 1 1 1 1 1 1 2. There are 9 possible combinations here (the 2 can be in any position)

Then the next one: 1 1 1 1 1 1 2 2. There are 7 + 6 + 5 + 4 + 3 + 2 + 1 = 28 combinations.

So that is 38 so far. Carry on for the others ...

That is a shame. I often use and recommend Google Translate. It is obviously not perfect!

I think you want to say "in pairs" or "pairwise" or "two at a time".

Two at a time.

That's my mean.

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