Salt flows into the tank at a rate of
(1/2 lb/gal) * (6 gal/min) = 3 lb/min
and flows out at a rate of
(Q(t)/60 lb/gal) * (6 gal/min) = 6Q(t) lb/min
The net rate of change of the amount of salt in the tank at time is then governed by
Solve for :
The tank starts with 10 lb of salt, so that Q(0) = 10. This gives us
so that the amount of salt in the tank at time is given by
I have attached a diagram of the triangle described.
We can use any of the trigonometric functions to find angle x. Remember, SOH CAH TOA. And since we're finding the angle, we'll need to use an inverse trigonometric function. For this problem, I'll be using the sine function.
sin(x) = 84 / 85
x = sin^-1(84/85)
x = 81.2026 degrees (feel free to round to however many places you need)
Hope this helps!! :)
