Answer:
forever (no solution)
Step-by-step explanation:
If the figure you're working with is the one shown below, no amount of mixing will reduce the solid content to 35%.
The vessel contains 40% solids.
The incoming feed is ...
(100 kg/h)×(60% solids) = 60 kg solids/h
out of a total influx of material of ...
(100 kg/h +70 kg/h) = 170 kg/h
That means the solids content of the inflow is ...
(60 kg)/(170 kg) = 0.352941 ≈ 35.3%
The solids content cannot ever be less than 35.3%. The problem has no solution.
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We suggest you discuss this question with your teacher to see how they would solve it.