SOLUTION: Rachel is driving to an appointment. at her current speed she will be 11 minutes late and her destination is still 68 miles away. she increses her speed by 6 miles per hour and arr

Algebra.Com
Question 904999: Rachel is driving to an appointment. at her current speed she will be 11 minutes late and her destination is still 68 miles away. she increses her speed by 6 miles per hour and arrives on time. what was her original speed?
Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!
r original speed
68/r -68/(r+6) = 11/60 hr |Multiplying thru by r(r+6) so as all denominators = 1
68*6 = (11/60)r(r+6)
11r^2 +66r - 60*68*6 = 0 (Tossing out the negative solution for unit measure)
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation (in our case ) has the following solutons:



For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=1081476 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: 44.2700174048471, -50.2700174048471. Here's your graph:
RELATED QUESTIONS

Sina has an appointment at 11:15 40 km from her home. She averaged 60km/h for the trip... (answered by josmiceli)
when a bicyclist is 20 km from her destination she realizes that she will be 10 minutes... (answered by ikleyn)
Hi, Every day Rachel walks 20 km at a certain speed. One day Rachel left 30 minutes late (answered by josgarithmetic,MathTherapy)
Sina has an appointment at 11:15, 40 km from her home. She averaged 60km/h for the trip... (answered by Iluvidina)
Gina has an appointment in 45 min. She is driving at a rate of 30 mi/h. If the... (answered by josgarithmetic)
Gina has an appointment in 45 min. She is driving at a rate of 30 mi/h. If the... (answered by josgarithmetic,MathTherapy)
Vivian is walking to the hair dresser’s at 1.0 m/s when she glances at her watch and... (answered by ikleyn)
If Gina leaves now and drives at 66 km/h, she will reach Alton just in time for her... (answered by checkley71)
If Gina leaves now and drives at 66 km/h, she will reach Alton just in time for her... (answered by mananth)