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6) A boat traveled 80 miles downstream and back. The trip downstream took 5 hours. The trip back took

10 hours. What is the speed of the boat in still water? What is the speed of the current?

User MrCarrot
by
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1 Answer

4 votes

Answer:

  • 12 mph and 4 mph

Explanation:

  • Let the speed of the boat = b and the speed of the current = c

Equations to reflect time, time = distance/speed:

  • Downstream
  • 80/(b + c)= 5 ⇒ b - c = 80/5 ⇒ b + c = 16
  • Upstream
  • 80/(b - c) = 10 ⇒ b - c = 80/10 ⇒ b - c = 8

Sum of the 2 equations above

  • b + c + b - c = 16 + 8
  • 2b = 24
  • b = 12
  • c = 16 - 12 = 4

So the speed of the boat is 12 mph

The speed of the current is 4 mph

User Lostaman
by
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