Secondary Level question

I've got a question on different number combinations.....If you have the digits 0235588 how many different combinations can you possibly form with these seven digits? I would like to know both the answer of how many different combinations there are and how you would go about setting the equation up to solve this.



Hi Blake,

Suppose that the symbols you have are 0235x8y. How many combinations can you form with these 7 symbols? Suppose that you have a list of all of them. Two such combinations would be 253x0y8 and 2x350y8. But x is 5 so these supposedly two combinations, 253x0y8 and 2x350y8, are actually the same one, 25350y8. In fact, in your list of all combinations of the symbols 0235x8y every one has a twin, just interchange the 5 and the x. Hence your list is twice as long as it should be.

Now apply the same argument to the 8 and the y.