SOLUTION: Two boats leave the same dock in Cairo at the same time. One heads north on the Mississippi River while the other heads south. The northbound boat travels three miles per hour. The

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Question 1191104: Two boats leave the same dock in Cairo at the same time. One heads north on the Mississippi River while the other heads south. The northbound boat travels three miles per hour. The southbound boat goes nine miles per hour. How many hours will it take them to be 42 miles apart?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
They are moving away from each other at 3%2B9=12 miles per hour.
x, how much time until distance between them is 42 miles

12x=42
2x=7
x=7%2F2
x=3%261%2F2hours