I am still unsure how to read the meaning of your question.

Do you mean that only the five digits are in correct order?

Or would you count 129348567 because the first seven are correct?

Results 1 to 5 of 5

- Nov 12th 2007, 11:44 AM #1

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## Little help please

here is the question.

The number 916238457 is an example of a nine-digit number which

contains each of the digits 1 to 9 exactly once. It also has the property

that the digits 1 to 5 occur in their natural order,while the digits 1

to 6 do not. How many such numbers are there?

I am having difficult implementing the last clause to get a complete solution.

all help is appreciated. Thank you in advance.

- Nov 12th 2007, 11:59 AM #2

- Nov 12th 2007, 12:01 PM #3

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- Nov 12th 2007, 12:20 PM #4
O.K. then.

Think of _1_2_3_4_5. We can put the ‘6’ in any of those places. That is 5 ways.

Say we choose _1_2_6_3_4_5_. Now there are seven places to put the ‘7’. That is 7 ways.

There are then 8 ways to put the ‘8’ and then nine ways to place the ‘9’.

What is the total number of ways?

- Nov 12th 2007, 12:25 PM #5

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