SOLUTION: it took Miguel 3.5 hours to drive from city a to city b. on his way back to city a, he increases his speed by 20 km per hour and it took him 3 hours. find the average speed for the

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: it took Miguel 3.5 hours to drive from city a to city b. on his way back to city a, he increases his speed by 20 km per hour and it took him 3 hours. find the average speed for the      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1070839: it took Miguel 3.5 hours to drive from city a to city b. on his way back to city a, he increases his speed by 20 km per hour and it took him 3 hours. find the average speed for the whole journey
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
              SPEED       TIME      DISTANCE
A to B         r          3.5       d=(r)(3.5)
B to A        r+20        3         d=(3)(r+20)
Totals                   6.5       3.5r+3r+60


-
3.5r=3r%2B60
0.5r=60
highlight_green%28r=120%28kilometers%2Fhour%29%29
-

WHOLE JOURNEY, average speed:
%286.5%2A120%2B60%29%2F6.5

highlight%28129%28kilometers%2Fhour%29%29