Call the rate in still water vs;
upstream you have: vs-v=6/4
downstram you have: vs+v=6/3
where v is the rate with which the river flows.
rearranging:
vs-v=3/2
vs+v=2
from the second you have v=2-vs substitute into the first:
vs-2+vs=3/2
2vs=7/2
vs=7 mi/hr
You can easily use online calculators for this.
Steps:
1) Find radius. 45 / 2 = 22.5
2) Substitute values (r) and (h) in the formula for surface area of a cylinder:
SA = 2πr² + 2πrh
3) Solve the formula.
You should end up with 9542.59 units². This answer is using π.
To get the answer with (3.14), do the steps above.
