Question 982332
Since 15'={{{(15/60)^o=0.25^o}}} , 35°15'={{{35.25^o}}}
The boat goes from point A to point B in 3 hours {{{drawing(280,380,-2,12,-2,17,
triangle(0,0,11.08,0,0,15.68),
rectangle(0,0,0.8,0.8),
locate(5.6,8.5,19.2km),
red(circle(0,15.68,0.1)),locate(0.2,16.5,red(L(lighthouse))),
green(circle(0,0,0.1)),locate(-0.1,-0.2,green(B)),
green(circle(11.08,0,0.1)),locate(11,-0.2,green(A)),
red(arrow(11.08,0,11.08,15)),locate(11.2,15.8,red(N)),
green(arrow(11.08,0,-1.4,0)),locate(-1.9,0.3,green(W)),
red(arc(11.08,0,10,10,-125.25,-90)),locate(8.5,4.8,red(35.25^o)),
red(arc(0,15.68,10,10,54.75,90))
)}}}
The right triangle in the illustration tells us that the distance from A to B is
{{{(19.2km)*sin(35.25^o)=about11.08km}}} .
That makes the speed of the boat
{{{11.08km/"3 hours"=3.7}}}{{{"km / h"}}} (rounded).