SOLUTION: A certain trip takes 40 minutes. If half the distance is travelled at an avg speed of 100km/h and the other half at an avg speed of 60km/h, what was the distance travelled during t

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A certain trip takes 40 minutes. If half the distance is travelled at an avg speed of 100km/h and the other half at an avg speed of 60km/h, what was the distance travelled during t      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 849732: A certain trip takes 40 minutes. If half the distance is travelled at an avg speed of 100km/h and the other half at an avg speed of 60km/h, what was the distance travelled during the trip.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +t+ = time for the 1st half of the trip
+40%2F60+-+t+ = time for the 2nd half of the trip
(1) +d%2F2+=+100t+
(2) +d%2F2+=+60%2A%28+40%2F60+-+t+%29+
----------------------------
(1) +d+=+200t+
(2) +d%2F2+=+40+-+60t+
(2) +d+=+80+-+120t+
----------------------
Substitute (1) into (2)
(2) +200t+=+80+-+120t+
(2) +320t+=+80+
(2) +t+=+1%2F4+
and
(1) +d+=+200t+
(1) +d+=+200%2A%281%2F4%29+
(1) +d+=+50+
The distance traveled is 50 km
check:
(2) +50%2F2+=+60%2A%28+40%2F60+-+1%2F4+%29+
(2) +25+=+40+-+15+
(2) +25+=+25+
OK