Sunday, March 9, 2008

Time & Distance Problem 3 Solution

In this problem its important to know that if you're moving a certain speed and someone else is moving another speed, the distance being covered between the both of you is the same as if you were going the added speeds yourself. In other words, if you're moving 20 miles per an hour and someone else moving towards you is going 60 miles an hour then the amount of distance being crosses is at the rate of 80 miles an hour.

Another way of looking at is if there's 800 miles between you and someone else, the 1st hour you went 20 miles (20 mi/hr) and they went 60 miles (60 mi/hr) or 80 miles total of the distance. Which you can see 2 things from. 1) It would take 10 of those hours 80 X 10 = 800 to go 800 miles and 2) You can just add the speeds 60 mi/hr + 20 mi/hr to get 80 mi/hr and figure out how long it would take you to go 800 miles.

So algebraically: 20x + 60x = 800
80x + 800
x = 800/80 = 10

So, in this problem it would take 10 hours for Bob and Steve to meet.

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