Quote:
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Originally Posted by GirlNinja
2. Two cars leave St. Louis from exactly the same spot at exactly the same time, one traveling west at 60 mph and the other traveling east at 40 mph. How long does it take before the cars are 180 miles apart?
A. 1 hour 18 minutes
B. 1 hour 28 minutes
C. 1 hour 38 minutes
D. 1 hour 48 minutes
E. 2 hours
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I would say "D"...
Here is how I got it:
You don't know the amount of time so call that 'x'
one car going 40mph and the other going 60mph and a total of 180miles
so
(40MPH *Time(X)) + (60MPH *Time(X)) = 180 miles
40X + 60X =180
100X = 180
X=1.8hours
0.8 hours equals 48minutes (0.8 X 60) so total time is 1.8hours or 1hour and 48minutes
Proof: (40)1.8 + 60(1.8) = 180miles
That means 40MPH car went a total of 72miles and the 60MPH car went 108miles = Total distance apart is 180miles
Hope this helps..
B-