AQA Core 4 5.05 Forming a Differential Equation

[numbertwentyseven]

could you do more of this subject please? it'd be of great help.

[miano]

For the right hand side, why don't you add a t (for e.g. dA/dt =At (9-At)) since it states that at time t hours the affected surface area is A m^2? Thanks

[edwarda.]

could you please explain when you would have a 1 over k differential equation or a negative k differential equation?

[MongooseOwen]

Is there any other videos of forming a differential equations from words that u have done for other exam boards or papers that expand on this type of problem?

[WaqasK-Khan]

How would you separate the variables in this case after forming the differential equation?

[junz]

Which exam board did this question come from?