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1) How many three-digit numbers more than 600 can be formed by using the digits $2,3,4,6,7$?

2) How many number greater than a million can be formed with the digits $2,3,0,3,4,2,3$?

How could I distinguish between a repetition and non repetition permutation question?

E.g.: In first question repetition of digits is allowed, but in second repetition is not allowed (e.g. it can't have $3333333$).

Note: Please explain me how can I guess whether a question involves repetition or not,in general not only on this specific question.

Jendrik Stelzner
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J.Doe
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    On 1): the first digit must be $6$ or a $7$ (so $2$ choices). For the second and third there are $5$ choices. So $2\times5\times5$ numbers in total. – drhab Sep 09 '18 at 17:19
  • @drhab Note: Please explain me how can I guess whether a question involves repetition or not,in general not only on this specific question.I already know how to solve this question. – J.Doe Sep 09 '18 at 17:21
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    Sorry, but I cannot really help you with that. Also for me every time I encounter a problem in that context I must wonder: "what exactly is allowed and what is not?" Others will have that too, and it might explain why your question on that has not been answered. – drhab Sep 09 '18 at 17:23
  • @drhab Thanks sier,for paying attention towards my question!! – J.Doe Sep 09 '18 at 17:26
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    I suspect that in both questions repetition of digits is not permitted since the questions do not explicitly state that repetition is permitted. In the second exercise, you may use each digit the number of times it appears in the list. – N. F. Taussig Sep 09 '18 at 17:46
  • @N.F.Taussig no sir in my textbook----- first question repetition of digits is allowed, but in second repetition is not allowed – J.Doe Sep 09 '18 at 17:53
  • @N.F.Taussig sir what's the general way to know it in any question – J.Doe Sep 09 '18 at 17:53
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    It sounds like you would benefit from reading a more carefully written textbook. It should be the responsibility of the author to make clear whether repetition is permitted. Your request is a result of the failure of the author of your textbook to do that. – N. F. Taussig Sep 09 '18 at 19:41

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