SOLUTION: If Kevin walks to school and rides his bicycle back home it takes him 90 minutes. If he rider his bicycle both ways it takes him 30 minutes. How would it take him to make the tri

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Question 615427: If Kevin walks to school and rides his bicycle back home it takes him 90 minutes. If he rider his bicycle both ways it takes him 30 minutes. How would it take him to make the trip to school and back walking both ways?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +d+ = the one-way distance from home to school
Let +w+ = his speed walking
Let r+ = his speed riding
Let +t+ = his time walking one-way
------------------------
Walking and riding:
+d+=+w%2At+
+d+=+r%2A%28+1.5+-+t+%29+
---------------
Just riding:
+2d+=+r%2A.5+
-----------
It doesn't really matter what I say the distance is.
No units of speed or distance are given. I will say
the distance is +1+ unit of length and the speeds
are units/hour.
--------------
(1) +1+=+w%2At+
(2) +1+=+r%2A%28+1.5+-+t+%29+
(3) +2+=+.5r+
-------------
(2) +1+=+1.5r+-+r%2At+
and
(3) +r+=+2%2F.5+
(3) +r+=+4+ units/hr
and
(2) +1+=+1.5%2A4+-+4t+
(2) +4t+=+6+-+1+
(2) +4t+=+5+
(2) +t+=+1.25+ hrs
-------------
(1) +1+=+w%2A1.25+
(1) +w+=+.8+ units/hr
--------------
+2%2A1+=+w%2A%282t%29+
+2t+=+2%2Fw+
+2t+=++2%2F.8+
+2t+=+2.5+
It will take him 2.5 hrs walking both ways
-------
check:
(2) +1+=+1.5r+-+r%2At+
(2) +1+=+1.5%2A4+-+4%2A1.25+
(2) +1+=+6+-+5+
+1+=+1+
OK