Question

Couipaiy 27, A large tank is partially filled with 400 L of fluid in which 5 kg of salt is dissolved. Brine containing 0.25 kg of salt per liter is pumped into the tank at a rate of 20 Lmin. The well-mixed solution is then pumped out at a slower rate of 15 L/min. Find the number of kilograms of salt in the tank after 30 minutes.

Answer 1

Thus o. tind Ri and R.-rft ti - canentratron of Salt in lhflo»). (inp«t rate »f Lir*) 0.25 min in Since the solution is pumped out a slower the of wate in the tant accumulate s 4he amount thus at the rate of (20-15). 5 LI-nin. (400 + 5t) L in tank. Thus afte,-t' minutes there will b 5 L min (400 +5t) ALt) 80+ヒ 4oo St Uouo oe subetitute these resalts in the de to e ALt) dt r Dt in the Standard- ohich is a linea Thus, tha ïnteg ating factor In (t+»») dt

lou» «pelrng -the initial condition, Alo)- 5 C 400 80 so, after 오0 min l6o+ 2Co) - 133.18 k4