it woud be :
person 1: ساعت چند است؟
person 2 : (pm==سه و بیست و چهار دقیقه (بعد ظهر
this was in formal way
but in speech we say:
person 1 : ساعت چنده؟
person 2 : سه و نیم
notice that i round the minutes. it's common in every language :)
نیم have the exact meaning of half