C4 Differentials

How do you do part b)?

I tried $400 = 1600-k\sqrt{25}$ but that doesn't give me the required $0.02$

I think it will work if you work out $\dfrac{dh}{dt}$ when $\dfrac{dV}{dt} = 400$ and then work out k from there?

that would give $\dfrac{dh}{dt}= \dfrac{1}{4000}\ *\ 400$ which $=0.1$

Hmm..

Yeah for some reason I don't think that works either >.>

Do you happen to have the mark scheme? Either the question is wrong, or it's so obvious we'll kick ourselves!

Yes but I want to understand why it is so, mark scheme will just show me a bunch of numbers and calculations. I wont look at it for now

Yes but I want to understand why it is so, mark scheme will just show me a bunch of numbers and calculations. I wont look at it for now

Okay, I often find it easier to understand what the question wants from looking at the mark scheme. It's only 1 mark, so it can't be that hard. I don't know what paper this from, but 1 mark 'show' questions are normally 'verify' for me, which literally just means plug the numbers in and confirm the answer.

How do you do part b)?

I tried $400 = 1600-k\sqrt{25}$ but that doesn't give me the required $0.02$

The water is being poured in at a rate of $1600cm^3s^{-1}$ and it is leaking out at a rate of $400cm^3s^{-1}$... so what is the total rate of change of volume at that instant?

Dammit thank you <3