@acer Thank you! That was helpful.

A follow up question

I have a decimal number, for ecample 0.04572.

How can I find out the number of its decimal digits? Here it would 5.

@MapleMathMatt I solved the problem with your help. Thank you very much!

@Kitonum Thank you, very kind. My problem is, that in my lists L usually not all other elements differ from the elements in N; my lists L look like L1 and L2 in my examples. How could I solve that problem?

@MapleMathMatt Thats it! Thank you very much! Very impressing :)

@MapleMathMatt It is the goal to take a given number and see if it can be recreated from the legtover digots.

@Kitonum 

Thanks a lot. My example was not good. The repeats should not removed all. And then with the remaining digits in p' and q' should be checked, if another given number s and t can be created.

A better example is: p=245266, q=526676. Is it possible, with the remaining digits of p' to create the number s=42? And with the remaining digits of q' to create the number t=66?

p and q have the digits 2, 5, 6, 6 in common. For p' remain 2 and 4, for q' remain 6 and 7. So, The number r= 42 can created from 2 and 4, but not t=66 from 6 and 7.

Sorry for the circumstances!

Thank you very much.

@MapleMathMatt Thanks a lot. Good that you mention the repeats. My example was not good. The repeats should not removed all. And then with the remaining digits in p' and q' should be checked, if another given number s and t can be created.

A better example is: p=245266, q=526676. Is it possible, with the remaining digits of p' to create the number s=42? And with the remaining digits of q' to create the number t=66?

p and q have the digits 2, 5, 6, 6 in common. For p' remain 2 and 4, for q' remain 6 and 7. So, The number r= 42 can created from 2 and 4, but not t=66 from 6 and 7.

Sorry for the circumstances!

Thank you very much.

@Carl Love Tis was very helpful :)))

Thank you very much!

@mmcdara Thank you, that was helpful!

@sursumCorda Thank you, that was helpful!

@mmcdara Thank you, that was helpful!

@Kitonum Thank you, that was helpful!