At noon, ship a is 50 km west of ship
b. ship a is sailing south at 10 km/h and ship b is sailing north at 20 km/h. how fast is the distance between the ships changing at 4: 00 pm? (round your answer to one decimal place.) 23.05 incorrect: your answer is incorrect. km/h

Given: dA/dt=10 km/hr and dB/dt=20 km/hr
bade of the triangle is 50 km
we are required to find dD/dt when t=4 hr
(A+B)^2+50^2=D^2

d/dt((A+B)^2+50^2)=d/dt(D^2)
[d(A+B)]/dt2(A+B)(2)=dD/dt2D
A=10km/hr*4hr=40 km
B=20km/hr*4hr=80 km
(10+20)*(2)*(120)*(2)=2*√8000*dD/dt
dD/dt=7200/sqrt(8000)
80.5 km/hr