Don L. answered • 06/19/19

Fifteen years teaching and tutoring basic math skills and algebra

Hi In need of help, for the boat to arrive at the opposite shore directly opposite its starting point, the current in the river must equal the y-component of his upstream rate.

Since there is no reference to how the 20 degree angle is determined, I am using it based on the bank of the river where the boat started. If you determine the 20 degree angle based on the other bank of the river, you will get a different answer.

The upstream y-component is equal to: 15 * cos 20 degrees, or 14.09 km / hr.

Therefore, the river's current is 14.09 km / hr.

Questions?