Question

The speed of a stream is 4 mph a boat travels 3 miles upstream in the same time it takes to travel 11 miles downstream what is the speed of the boat in Stillwater

Answer 1

$\bf \begin{array}{lccclll} &distance&rate&time\\ &-----&-----&-----\\ upstream&3&r-4&t\\ downstrea&11&r+4&t \end{array}\\\\\\ recall\implies d=rt\\\\ -----------------------------\\\\ \begin{cases} 3=(r-4)(t) \\\\ 11=(r+4)(t)\\ --------------\\ 3=(r-4)(t)\to \frac{3}{r-4}=\boxed{t}\qquad thus \\\\ 11=(r+4)(t)\to 11=(r+4)\left( \boxed{\frac{3}{r-4}}\right) \end{cases}$

solve for "r"