+328 Driving at a constant speed, Sharon usually takes 180 minutes to drive from her house to her mother's house. One day Sharon begins the drive at her usual speed, but after driving 1/3 of the way, she hits a bad snowstorm and reduces her speed by 20 miles per hour. This time the trip takes her a total of 276 minutes. How many miles is the drive from Sharon's house to her mother's house?
Let her average speed for the first 1/3 of her drive==S
Let the distance between her house and her mother's house==D
D / S ==180 / 60
1/3D / S + 2/3D / (S - 20) ==276 / 60
S==45 mph - Her average speed.
D ==135 miles - distance between her house and her mother's house.
+118673 Let the entire distance be 3x
Normally that takes 180 minutes
speed would be (3x)/180 = x/60 miles per minute
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Storm day
It would take 60 minutes to go the first distance of x
then
276-60 = 216 minutes to go the next leg of 2x
speed is \(\frac{x}{60}-\frac{20}{60}=\frac{x-20}{60}\;miles\; per \;minute\)
speed = distance /time
\(\frac{x-20}{60}=\frac{2x}{216}\\ \frac{x-20}{60}=\frac{2x}{27*8}\\ \frac{x-20}{10}=\frac{x}{18}\\ 18x-360=10x\\ 8x=360\\ x=45 miles\\ Total \;\;distance = 3*45 = 135miles.\)
