how far must you swim upstream to get directly in front of a pizza stand .2 km away on the other side of a river if you can swim 4km/hr and the river moves downstream at 1.5km/hr

Answer 1

Draw the diagram. You have a right triangle with the upstream leg = 1.5 and hypotenuse 4.
Thus, the distance across is √(4^1-1.5^2)=3.7

But you have to scale the triangle so the cross-stream distance is only 0.2, so the new upstream leg will be

0.2/3.7 * 1.5 = 0.08 km

Answer 2

The emf produced in a generator is Vemf=25sin377t. What is the frequency of rotation of the circular coil?
50Hz
60Hz
25Hz
15Hz