Learn Dutch: Ik weet niet waarmee het meisje knipt. - I do not know what the girl is cutting with.

In Dutch, when you combine a preposition (like met) and the question word wat to ask about a thing, they merge into waar + preposition. This forms a pronominal adverb. Therefore, met + wat becomes waarmee (literally "where-with"). Note that if you were asking about a person, you would just use met wie (with whom).

Why does the preposition met change to mee in the word waarmee?

A few Dutch prepositions change their spelling when they attach to waar-, daar-, or hier-. The preposition met (with) always changes to mee, giving us waarmee instead of "waarmet". Another common example you might see is tot changing to toe.

Why is the verb knipt pushed to the very end of the sentence?

The first part of the sentence (Ik weet niet) is the main clause. The word waarmee introduces a subordinate clause (a dependent clause that cannot stand alone as a full sentence). In Dutch subordinate clauses, the conjugated verb is always pushed to the end, which is why knipt comes after the subject het meisje.

Just to review: why do we say het meisje instead of ?