SOLUTION: The speed of a river is 4 mph. A boat travels 3 miles upstream (against the current) in the same amount of time it takes to travel 11 miles downstream (with the current). Find the
Algebra ->
Polynomials-and-rational-expressions
-> SOLUTION: The speed of a river is 4 mph. A boat travels 3 miles upstream (against the current) in the same amount of time it takes to travel 11 miles downstream (with the current). Find the
Log On
Question 930543: The speed of a river is 4 mph. A boat travels 3 miles upstream (against the current) in the same amount of time it takes to travel 11 miles downstream (with the current). Find the speed of the boat in still water (no current). Answer by TimothyLamb(4379) (Show Source):
You can put this solution on YOUR website! x = speed of boat in still water
y = speed of current = 4 mph
---
s = d/t
t = d/s
---
upstream:
t = 3/(x - y)
t = 3/(x - 4)
---
downstream:
t = 11/(x + y)
t = 11/(x + 4)
---
equate times:
3/(x - 4) = 11/(x + 4)
3(x + 4) = 11(x - 4)
3x + 12 = 11x - 44
8x = 56
x = 56/8
x = 7
---
answer:
x = speed of boat in still water = 7 mph
---
Solve and graph linear equations:
https://sooeet.com/math/linear-equation-solver.php
---
Solve quadratic equations, quadratic formula:
https://sooeet.com/math/quadratic-formula-solver.php
---
Convert fractions, decimals, and percents:
https://sooeet.com/math/fraction-decimal-percent.php
---
Calculate and graph the linear regression of any data set:
https://sooeet.com/math/linear-regression.php
