Lizzy: Peter has to walk 2.5 miles to get to the grocery store. If it takes him 20 minutes to walk one mile and he has walked 1 mile already, how many more minutes does he have to walk to reach it?.
Me: Hmmm, let me think. I think this is the detailed solution:
Peter has to walk a remaining 2.5 total miles - 1 mile completed = 1.5 miles remaining. It will take him another 20 minutes * 1.5 miles remaining = 30 minutes to get to the grocery store. Final answer: 30.