Learn Spanish (Latin America): El mayorista vende la mitad del lote.

La mitad is a noun meaning "the half," and it is used with de (of) to specify the whole. Since lote is masculine (el lote), de and el combine to form the contraction del. You could use the adjective medio to say medio lote (half a lot), but la mitad del lote (half of the lot) is more common when referring to a specific, defined batch.

How would I change this sentence to say the wholesaler sells "double the lot" or "a third of the lot"?

You can swap la mitad for other quantity nouns from this lesson while keeping the del (de + el). For example, use el doble for "double" (El mayorista vende el doble del lote) or un tercio for "a third" (El mayorista vende un tercio del lote).

Why is it El mayorista when the word ends in -a?

Nouns ending in -ista (like many professions or roles) have the exact same form for both masculine and feminine. The article tells us the gender. El mayorista refers to a male wholesaler, while la mayorista would be a female wholesaler.

Does lote here mean "a lot" as in "a lot of things"?