+0  
 
0
106
1
avatar

Jill drove the 200 miles to Cincinnati at an average speed of 10 miles per hour faster than her usual average speed. If she completed the trip in 1 hour less than usual, what is her usual driving speed, in miles per hour

 Mar 16, 2020
 #1
avatar+25883 
+1

Normal speed = x

xt = 200      t = 200/x

 

 

faster speed    (x+10 )    new time = t-1   = 200/x -1

 

(x+10)(200/x -1) = 200 miles

200 -x + 2000/x -10 = 200

-x  + 2000/x -10 = 0

-x^2 + 2000 - 10 x = 0       via quadratic formula   x = 40 m/hr

 Mar 16, 2020

23 Online Users

avatar
avatar