Question

a motor boat has two throttle position on its engine . The high speed position propel the boat at 30km/h in still water and the low speed position gives one tired the higher speed . The boat moves from its dock downstream on a river with the throttle at low speed position and return to the dock with throttle at high speed position . The return trip took 5% longer time that it did for the downstream trip . Determine the velocity of flow of river .

Answer 1

$$\begin{gathered} Letthevelocityofflowofriverbev. \\ Thedownstreamtripmotion \\ 10+v=\frac{x}{t}-----\left(1\right) \\ andupstreamtripmotion \\ 30-v=\frac{100x}{105t}-------\left(2\right) \\ fromeqns\left(1\right)and\left(2\right) \\ \frac{30-v}{10+v}=\frac{100}{105} \\ or3150-105v=1000+100v \\ or205v=2150 \\ orv=\frac{2150}{205}=10.5Km/h\left(approximately\right) \end{gathered}$$