Questions & Answers about Tyttö on piirtänyt kuvan, ja poika on neulonut sukan.
How do we form the past participle forms piirtänyt and neulonut from their dictionary forms?
Both piirtää (to draw) and neuloa (to knit) are Type 1 verbs. For Type 1, you simply drop the final -a or -ä and add -nut or -nyt. Because of vowel harmony, piirtää uses the front-vowel ending to become piirtänyt, while neuloa uses the back-vowel ending to become neulonut.
Why is it piirtänyt with a strong rt, when 'I draw' is piirrän with a weak rr?
For Type 1 verbs, the active past participle (the -nut or -nyt form) always uses the strong consonant grade, exactly like the dictionary form (infinitive). So it keeps the rt from piirtää. You only use the weak grade for personal endings like 'I' (piirrän) or 'you' (piirrät).
How is the perfect tense built in this sentence?
The perfect tense describes actions that happened in the past but still connect to the present. You form it by using the auxiliary verb olla (to be) in the present tense, followed by the active past participle of your main verb. Here we have on (is) plus piirtänyt (drawn), and on (is) plus neulonut (knitted).
Why do the words for picture (kuva) and sock (sukka) end in -n here?