I should know this… At 4 miles per hour, it takes exactly one hour for Abe to walk to school in a blinding blizzard. How many minutes would it take for him if he were to walk at 5 miles per hour? I already know the answer (48 minutes), but I am wondering how you get this number. I feel so stupid! I’m just having one of those blank-out moments!
Anyways, I would appreciate input on this problem.

Thank you!

I find the easiest way to approach these problems is with a pair of ratios, along with a little assumption to make life easier (you can in this case).
Assume that his house is exactly 4 miles away from school; it doesn’t matter exactly how far he is since he’s walking at a constant rate.
With this assumption, we know that it will take him 1 hour to get to school.
Speed = distance/time = 4 miles/1 hour = 4 miles/60 minutes

If he walks at 5 miles per hour,
5 miles/ 60 minutes = 4 miles/x minutes, where x is the time it will take Abe to get to school. –> (he walks at a constant speed so we want to keep the ratio the same)
Using cross-multiplication, we get x minutes = (4 miles) * (60 minutes) / (5 miles) = 48 minutes (the units for miles cancels out).

Thus is takes him 48 minutes to get to school.

I know what that feels like; it’s so annoying when it happens. Hope this helps!

3 Responses

1. maggikate Says:
   January 18th, 2010 at 10:33 am

   4 miles per hour = 1 mile per 15 minutes

   5 miles per hour = 1 mile per 12 minutes
   References :

2. moogles_rule Says:
   January 18th, 2010 at 10:43 am

   I find the easiest way to approach these problems is with a pair of ratios, along with a little assumption to make life easier (you can in this case).
   Assume that his house is exactly 4 miles away from school; it doesn’t matter exactly how far he is since he’s walking at a constant rate.
   With this assumption, we know that it will take him 1 hour to get to school.
   Speed = distance/time = 4 miles/1 hour = 4 miles/60 minutes

   If he walks at 5 miles per hour,
   5 miles/ 60 minutes = 4 miles/x minutes, where x is the time it will take Abe to get to school. –> (he walks at a constant speed so we want to keep the ratio the same)
   Using cross-multiplication, we get x minutes = (4 miles) * (60 minutes) / (5 miles) = 48 minutes (the units for miles cancels out).

   Thus is takes him 48 minutes to get to school.

   I know what that feels like; it’s so annoying when it happens. Hope this helps!
   References :

3. Sandy P Says:
   January 18th, 2010 at 11:15 am

   . Divide 5 miles an hr. in to 60 min = 12 .Then subtract 12 from 60 min. = 48 min.
   References :

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