How much time is that?

"Mom?" B asked. "Is 30 minutes an hour?" "Nope," Simone replied absently as she chopped some celery. "Thirty minutes is half an hour." "Oh." B considered this for a moment. "So 60 minutes equals an hour?" "Yes," Simone stopped chopping and paid more attention. "Okay. So is 110 minutes equal to two hours?" "Almost two hours," Simone corrected, glad she'd stopped chopping. Knives and math don't mix well with her. "Ah, okay. I get it," B smiled. "120 minutes makes two hours." "That's right," Simone beamed. "And 180 minutes makes three hours. 240 minutes is four hours?" Yup. Not bad for a six year old...