SOLUTION: To get to work Sam jogs 3 kilometers to the train, then rides the remaining 5 kilometers. If the train goes 40 km per hour faster than Sam's constant rate of jogging and the enti

Question 103605This question is from textbook Precalculus
: To get to work Sam jogs 3 kilometers to the train, then rides the remaining 5 kilometers. If the train goes 40 km per hour faster than Sam's constant rate of jogging and the entire trip takes 1/2 hour how fast does Sam jog? This question is from textbook Precalculus

Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
To get to work Sam jogs 3 kilometers to the train, then rides the remaining 5 kilometers. If the train goes 40 km per hour faster than Sam's constant rate of jogging and the entire trip takes 1/2 hour how fast does Sam jog?
:
Let s = his jogging speed
then
(s+40) = train speed
:
Write a time equation: Time = Distance/speed
:
jog time + train time = .5 hrs
+ = .5
:
Multiply equation by s(s+40) and you have:
3(s+40) + 5s = .5(s(s+40))
:
3s + 120 + 5s = .5s^2 + 20s
:
8s + 120 = .5s^2 + 20s
:
0 = .5s^2 + 20s - 8s - 120
:
.5s^2 + 12s - 120 = 0; a quadratic equation
:
Use the quadratic formula to find s: a=.5; b=12; c=-120

:
s = -12 + 19.5959; we only need the positive solution here
:
s = +7.5959 km/hr is his jogging speed
:
:
Check solution by finding the time
+ =
.394 + .105 = .499 ~ .5 hrs
:
Did this make sense to you? Any questions?
RELATED QUESTIONS
A train travels 150 kilometers in the same time it takes a plane to travel 400... (answered by checkley71)

A train travels at a constant speed of 125 kilometers per hour. How many minutes does it (answered by richwmiller,ewatrrr)

If a train travels 500 kilometers per hour. And the distance between the two cities your... (answered by ewatrrr)

If a train travels 128 kilometers in 1 1/3 hours .what is the average speed in kilometers (answered by ikleyn)

If I drive 80km at 20kmph and then 60km at 30 kmph how fast must I drive the remaining 40 (answered by Mathtut)

a train is traveling north at 95 km/hr. how long does it take to get to the station, if... (answered by ikleyn)

If a train 1 kilometer long is passing through a tunnel 7 kilometers long at a speed of... (answered by mananth)

Maria�took�a�trip�to�visit�her�grandmother.�She�traveled�first�by�train�at�80�kilometers (answered by stanbon)

Train A leaves a station � hour ahead of train B. the trains travel on parallel tracks. (answered by dkppathak)