I don't really agree with Elodie, to me, "elle ont une demie heure à manger" doesn't mean a thing if there's no other verb after "ont" For instance: "elles ont passé une demie heure à manger" (they have spent half an hour eating) or "elles ont mis une demie heure à manger" is correct, otherwise "pour manger" fits better if it's about the time allowed they have to eat What do you think Elodie?

There isn't a big différence , but "elles ont une demie heure pour manger" means they have half an hour for eating (but if they have finish before , no problem), and "elles ont une demie heure a manger " is they have half an hour to eat, (so during half an hour they will eat)

Without any doubt: Elles ont une demi-heure POUR manger. DEMI: without -e and with hyphen --> une demi-heure You wrote it perfectly A MANGER : impossible - if you write this, you give the impression that you are going to eat those 30 minutes !!!!!! Kind regards. martine :)