In traveling from a dormitory to a certain city...

Hi AAPL,

We're told that a student travels from a dormitory to a city in the following way: the student went 1/5 of the way by foot, 2/3 of the way by bus, and the remaining 8 kilometers by car. We're asked for the total distance, in kilometers, from the dormitory to the city. This question can be solved in a couple of different ways. The Algebraic approach (the formula that you listed) would certainly work here. You can also get to the solution by TESTing THE ANSWERS.

Let's TEST Answer D: 90 km

IF... Total distance = 90km
1/5 on foot = (1/5)(90) = 18km
2/3 by bus = (2/3)(90) = 60km
Remaining distance = 90 - 18 - 60 = 12km
This is TOO BIG (it's supposed to be 8km), so the total distance has to be LESS than 90km. The remaining distance was relatively close to 8km though, so we should look for the next largest answer....

Let's TEST Answer C: 60 km

IF... Total distance = 60km
1/5 on foot = (1/5)(60) = 12km
2/3 by bus = (2/3)(60) = 40km
Remaining distance = 60 - 12 - 40 = 8km
This is an exact match for what we were told, so this MUST be the answer.

Final Answer: C

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