SOLUTION: Imogene's car traveled 420 mi averaging a certain speed. If the car had gone 10 mph faster, the trip would have taken 1 hour less. Find the average speed.

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Question 974549: Imogene's car traveled 420 mi averaging a certain speed. If the car had gone 10 mph faster, the trip would have taken 1 hour less. Find the average speed.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
generalizing the description with variables,
Imogene's car traveled d miles averaging a certain speed. If the car had gone k mph faster, the trip would have taken h hour less. Find the average speed, r.


_______________________rate______________time______________distance
Certain________________r_________________t_________________d
IfFaster_______________r+k_______________t-h_______________d

KNOWN
h, k, d

UNKNOWN
r, t

BASIC RELATIONSHIP, EQUATION
RT=D relating rate, time, distance

SYSTEM OF EQUATIONS
system%28rt=d%2C%28r%2Bk%29%28t-h%29=d%29

Solve the system for r and t.

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

Imogene's car traveled 420 mi averaging a certain speed. If the car had gone 10 mph faster, the trip would have taken 1 hour less. Find the average speed.
Average speed: highlight_green%2860_mph%29