This achievement will unlock once you have an average word score of 20 points or more across all online games played, not just a single game after you have played your first 10 words.

If you've played the WP version a lot you may find you are quite a bit below the required 20 points average. I was on 14 average with around 110 games played and it took about an hour of only scoring 40+ points per word to reach 20 points average.

This can be checked in the statistics menu and is called 'Avg Move:'

Credit to Minioger for this info:

passing and swapping count as a move and decrease your average as they are 0 points!!

I ended up getting it by starting a game and getting a 20+ point word or resigning right away! Resigning doesn't hurt your average score (it doesn't count as a move).

EDIT: Credit to Humpurton for letting me know local games DO NOT count.

If you've played the WP version a lot you may find you are quite a bit below the required 20 points average. I was on 14 average with around 110 games played and it took about an hour of only scoring 40+ points per word to reach 20 points average.

This can be checked in the statistics menu and is called 'Avg Move:'

Credit to Minioger for this info:

passing and swapping count as a move and decrease your average as they are 0 points!!

I ended up getting it by starting a game and getting a 20+ point word or resigning right away! Resigning doesn't hurt your average score (it doesn't count as a move).

EDIT: Credit to Humpurton for letting me know local games DO NOT count.

nis the number of moves required):(expected average of future words - 20)n = 20(moves played) - (current average * moves played)

For example, if you expect to make 35 points from each future word, your current average is 15, and you've made 200 moves, the equation would look like the following:

(35 - 20)n = 20(200) - (15 * 200)

Which can be simplified as follows:

15n = 4000 - 3000

15n = 1000

n = 67 moves

I hope this helps!