<PRE><B>Question 561463</B>
Malik drove his car for 45 miles at an average speed of r miles per hour.
 On the return trip, traffic has increased and Maliks average speed is 3/4 r
 The round trip took a total of 1 Hour and 45 minutes.
 Find the average speed for each portion of the trip.
:
Change 3/4 to .75
Change 1 hr 45 min to 1.75 hrs
:
{{{45/r}}} + {{{45/(.75r)}}} = 1.75
multiply by 3r to clear the denominators, results:
3(45) + 4(45) = 3r(1.75)
135 + 180 = 5.25r
315 = 5.25r
r = {{{315/5.25}}}
r = 60 mph
then
.75(60) = 45 mph for the last part of the trip
;
:
Check this in the time equation
{{{45/60}}} + {{{45/45}}} =
.75 + 1 = 1.75 hrs</PRE>