Question 134561
Ken's running speed: x
Joe's running speed: 6 mph


Since we want to know about how fast Ken is running when he catches Joe, the distance they travel must be the same.


We also know that Joe is running for 30 minutes or one-half hour, and Ken is running for 20 minutes or one-third of an hour.



Joe's trip:
{{{d=6*(1/2)=3}}} miles


Ken's trip:
{{{d=x*(1/3)}}} and that must also equal 3 miles.


{{{x*1/3=3}}}


{{{x=9}}} miles per hour.


Check:
Joe: 6 mph for 1/2 hour = 3 miles
Ken: 9 mph for 1/3 hour = 3 miles