Levels 9-3 and 9-4 deal with verbs ending with -ing and -ed, some of which double their final consonant before the -ing or -ed ending. The words in level 9-3 are swimming, running, winning, throwing, washing, mailing, kicking, listening, hopping, and sitting. The words in level 9-4 are mixed, covered, enjoyed, compared, planned, tapped, dropped, tagged, stopped, and tipped. The general pattern here is that verbs which end with a short vowel + a single consonant will tend to have that final consonant be doubled when an -ing or -ed ending is added to the word.

We see that doubling pattern 11 times in the 20 words used in these two levels. Of the other 9 words, 7 of them don't need to double the final consonant because they already end with two consonants (kick, wash), they end with a vowel (compare), or their final vowel sound is a long vowel or vowel pair (enjoy, cover, throw, mail).

Two of these 20 words are oddballs: mixed and listening. By rule, those final consonants should double, but these two exceptions fail to do so. Alongside this lesson, you might want to show your students how other verbs ending in 'x' will generally break this doubling rule as well (boxing, taxed, fixed).