[quo]*Quote from * irene
- in the 2.1 Amy said: Para quantas personas?
I guess she used feminine gender here because it refer to her as a speaker, am I right?
but in the next question, why did she say: "Por quantos dias? instead of "Por quantas dias?"
In Spanish, nouns are either masculine or feminine. The gender often has very little to do with our stereotypical notions of masculinity or femininity. There are some rules of thumb to help you recognize whether a noun is masculine or feminine (e.g., most nouns ending in "o" are masculine, and most ending in "a" are feminine, but there are many exceptions). Adjectives that modify a noun have to agree with that noun in gender and number. Thus, Amy says "para cuantas personas" because personas is a feminine noun in the plural, and cuantas thus has to have a feminine plural form as well, since it modifies personas. In the next sentence, "cuantos" modifies "días," which is a masculine noun in the plural, and so "cuantos" takes a masculine plural form to agree with días.
Rocket Spanish comes with a number of valuable supplementary materials like the Beginner's Book, for example. I strongly recommend that you read it carefully. It (or other grammar books) should help you better understand what you're hearing in the audio files.