Terms for subject General containing need-to-know

English	Spanish
I know I was cheated, there is no need to rub it in	ya sé que me timaron, no hace falta que me lo restriegues
need to know	necesidad de conocer
there's no need for her to know	no hay necesidad de que se entere
We need to know from where the letter is	Necesitamos saber de donde procede  la carta
you need to know how to best combine these two flavours	hay que saber combinar estos dos sabores