Question 709290: Ken made the following successive trips on Interstate 80, an east- west road: 150 miles to the east, 170 miles to the west, 20 miles to the west, 43 miles to the east.
A) At the end of the forth trip, is ken east or west of his starting point?
B) How far must Ken go to return to his starting point?
Answer by jim_thompson5910(35256)   (Show Source):
You can put this solution on YOUR website! let east represent the positive direction, west represent the negative direction
so if he goes 150 miles east, then he's gone +150 miles
if he then goes 170 miles west, then he's gone -170 miles, so he is now 150+(-170) = -20 miles displaced from the starting point...in other words, he is 20 miles to the west of his starting point
Then he goes 20 more miles west, so his displacement is now -20 + (-20) = -40 miles (40 mi to the west)
Finally, he goes 43 miles east, so 43+(-40) = +3
This means that at the end of the forth trip, he's east of his starting point
Since he's 3 miles east of his starting point, he must go 3 miles west to return to his starting point. This is because 3 + (-3) = 0
Summary:
A) At the end of the forth trip, is ken east or west of his starting point?
East
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B) How far must Ken go to return to his starting point?
3 miles to the west
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