"Give the ball!"
why 'kan' is used with beri but not with lempar?
'-kan' can be used with both verbs.
With some verbs, there is no difference in meaning between me- / me-kan affix.
In the sentence above, you can use 'beri' / 'berikan'.
('berikan' sounds more natural to me).
That's another way to say it.
(informal version, used in daily speech, probably not accepted in this course).
Give the ball is 'berikan bolanya,' but throw the ball is 'lempar bolanya.'
It's the same for 'lempar' / 'lemparkan.
Lempar bolanya! = Lemparkan bolanya! <== same meaning.