Question 1015563: Kiran drove from Tortula to Cactus, a distance of 240 mi. She increased her speed by 8 mi/h for the 392 mi trip from Cactus to Dry Junction. If the total trip took 12 h, what was her speed from Tortula to Cactus?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Kiran drove from Tortula to Cactus, a distance of 240 mi. She increased her speed by 8 mi/h for the 392 mi trip from Cactus to Dry Junction. If the total trip took 12 h, what was her speed from Tortula to Cactus?
-------
T to C DATA::
dist = 240 miles ; rate = x mph ; time = d/r = 240/x hrs
--------
C to D DATA:
dist = 392 miles ; rate = x+8 mph ; time = d/r = 392/(x+8) hrs
------
Equation:
time + time = 12 hrs
240/x + 392/(x+8) = 12
------
240(x+8) + 392x = 12x(x+8)
------
240x + 1920 = 12x^2 + 96x
------
2x^2 - 144x - 1920 = 0
-----
x^2 - 72x - 960 = 0
x = 83.5 mph (speed from T to C)
------------
Cheers,
Stan H.
------------
|
|
|
