What is the correct pronounciation of пять? Because googletranslate pronounces it like "пэть" whereas duolingo here pronounces it like "пять"
Use Forvo when in doubt.
Why do we need the genitive (plural) here?
When counting, the case changes. The number ends with 1 = nominative singular. Ends with 2, 3, or 4 = genitive singular. 5 or more = genitive plural.