Question 312871
George is taking a road trip. Part of the trip will be highway driving at 100 
km/hr and part of the trip will be country roads driving at 60 km/hr.
The total trip will take 12 hours. How much time did he spend on each type of road?
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I don't think there is a unique solution if you don't know the length of the trip
:
Let x = dist running at 100km/hr
then
Let y = time running at 60km/hr
:
Write a time equation
{{{x/100}}} + {{{y/60}}} = 12
multiply by 600 to clear the denominators
6x + 10y = 12(600)
6x + 10y = 7200
10y = 7200 - 6x
y = 720 - .6x
pick a value for x, find y
x = 200 km (at 100 km/hr)
y = 720 - .6*200
y = 720 - 120
y = 600 km (at 60 km/hr)
:
Find the time for each:
200/100 = 2 hrs at 100 km/hr
600/60 = 10 hrs at 60 km/hr
:
Choose another value for x
x = 500 km
y = 720 - .6(500)
y = 720 - 300
y = 420 km
:
Find the time for each
500/100 = 5 hrs
420/60 = 7 hrs
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lots of solutions