Some d10 math

Average roll of 1d10: 5.5
Average roll of exploding d10: 6.11111111111
Average roll of two d10's (non-exploding) keeping just the highest die: 7.15

If I remember correctly from all the math I did back when I was playing 7th Sea, each unkept d10 (in a system where dice explode) raised the average roll of the dice by nearly 2 points.
So 1k1 averages 6, 2k1 (roll 2 dice and keep one) averages about 8, 3k1 averages around 10, 4k1 averages nearly 12, etc.
The math to prove this is more than I want to deal with right at the moment, as this post is purely a tangent to something else I was writing about. So take the above with a grain of salt. I'm pretty sure I worked it out and proved it, but that was 4 or 6 years ago, and I couldn't do so today without an hour or two of hair-pulling math to verify it.

Luckily,
a) there's a probability chart in the 7th Sea GMs guide to save you the trouble,
and
b) I'm not running 7th Sea right now so there's no need for me to work it out precisely.