It can have anywhere between 0 and 12 pairs of parallel sides.
The only arithmetic mean of 7 and 25 is (7+25)/2 =16. If you really mean all arithmetic means of all possible pairs of numbers between 7 and 25, then there are so many pairs you should clearly state so in your question. Or better still, just write them down, work them out and add them up, which is what I would have to do.
25 pairs, including the pair (2, 3).
the pairs are 1 x 25 5 x 5
It is not possible to list all the facts. For example, there are infinitely many pairs of numbers that sum to 25. Then there are infinitely many triplets of numbers that sum to 25. And infinitely many quartets, and so on. And that is only sums. There are infinitely many pair of numbers that multiply to 25, and infinitely many triplets and so on.
It can have anywhere between 0 and 12 pairs of parallel sides.
Two.
25
25
The only arithmetic mean of 7 and 25 is (7+25)/2 =16. If you really mean all arithmetic means of all possible pairs of numbers between 7 and 25, then there are so many pairs you should clearly state so in your question. Or better still, just write them down, work them out and add them up, which is what I would have to do.
Up to 12 pairs.
25 chromosomal pairs
12 pairs of ribs and 25 in the sternem
The factor pairs of 25 are 1 x 25 and 5 x 5
25 pairs, including the pair (2, 3).
1 and 25 5 and 5
The factor pairs of 25 are: 1 × 25 5 x 5