katy bicycle distance problem

Question

katy left her house on a bicycle heading north at 8mph.  At the same time her sister molly headed south at 12 mph.  How long will it take for them to be 24 miles apart?

Answer 1

Hi again Amie;

Katie, 8 m/h North

Molly, 12 m/h South

 

They are traveling away from each other at a rate of (8+12) m/h.

distance=(rate)(time)

(distance)/(rate)=time

(24 miles)/(20 miles/hour)=time

Let's cancel miles located in both the denominator in numerator...

(24 miles)/(20 miles/hour)=time

Let's note the fact that the unit of hour is a denominator within the denominator.  Henceforth, it is the numerator.

[(24)/(20)]hours=time

1.2 hours=time

Perhaps it would be better to express this in hours and minutes?

(1 hour)+(0.2 hours)=time

(1 hour)+[(0.2 hours)(60 minutes/1 hour)]=time

Let's cancel units where appropriate...

(1 hour)+[(0.2 hours)(60 minutes/1 hour)]=time

(1 hour)+(12 minutes)=time

 

NOW GET SOME SLEEP!