SOLUTION: A motorist travels a distance of 120 miles. Had she increased her average speed by 10 mi/hr she would have cut 36 minutes off of her travel time. Find her average speed.
Question 319987: A motorist travels a distance of 120 miles. Had she increased her average speed by 10 mi/hr she would have cut 36 minutes off of her travel time. Find her average speed. Found 2 solutions by mananth, MathTherapy:Answer by mananth(16946) (Show Source):
You can put this solution on YOUR website! let her speed be x
increased speed = x+10
distance traveled=120 miles
36/60 = 3/5 hours
..
time taken with increased speed= original time -3/5 hours
120/x+10= 120/x -3/5
120/x+10=600-3x /5x
5x*120=(x+10)(600-3x)
600x=600x-30x+6000-3x^2
3x^2+30x-6000=0
x^2+10x-2000=0
x^2+50x-40x-2000=0
x(x+50)-40(x+50)=0
(x+50)(x-40)=0
x=40 mph
You can put this solution on YOUR website! A motorist travels a distance of 120 miles. Had she increased her average speed by 10 mi/hr she would have cut 36 minutes off of her travel time. Find her average speed.
Let her average speed be S
Then we'll have: ----->
Multiply by LCD, 5S(S + 10) to get: 120(5)(S + 10) - 3S(S + 10) = 120(5S)
----- Dividing by GCF, 3
----- (S + 50)(S - 40) = 0
Ignoring the negative value (- 50), we get S, or average speed as: mph
