<PRE><B>Question 600779</B>
Joe walks 4 miles and jogs 7 miles in a total of 2 hours.
 If his jogging speed is twice his walking speed, how fast does he walk? 
:
Let w = his walking speed
then
2w = his jogging speed
:
Write a time equation, Time = dist/speed
:
walk time + jog time = 2 hrs
{{{4/w}}} + {{{7/(2w)}}} = 2
multiply by 2w
2w*{{{4/w}}} + 2w*{{{7/(2w)}}} = 2w(2)
Cancel out the denominators
2(4) + 7 = 4w
8 + 7 = 4W
15 = 4w
w = 15/4
w = 3.75 mph is his walking speed
then
2(3.75) = 7.5 mph is his jogging speed
:
:
See if that works, find the times
4/3.75 = 1.067 hrs
7/7.5 = .933
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Total: 2.0 hrs</PRE>