How many 6 digit number combinations will I have using 3,5,7,8? Using 5,7,8 each twice? Thanks

Question

How many different 6 digit number combinations will I have using 3,5,7 and 8. And using each number twice. List them?well. 

Answer 1

How many 6 digit number combinations will I have using 3,5,7,8? 

 

Problems of this kind are challenging, and I urge you to take up the challenge.

First off, in this problem there appear to be just four possible digits available, but there are no other limitations; obviously repetitions must be allowed. So just ask yourself: what could be put into the first digit position, and continue on for all remaining five digit positions. You will readily come up with an answer--solving it yourself from this suggestion is all that I as tutor should do.

 

The second problem is rather different, but is amenable to systematic tabulation of possibilities.