C3 rate of change question OCR

Hi
I am stuck on one question in an OCR C3 textbook.
Exercise 9B, Q7
A funnel has a circular top of diameter 20cm and height 30cm.
When the depth of the liquid in the funnel is 15cm, the liquid is dripping from the funnel at the rate of 0.2 cm^3 per second. at what rate is the depth of the liquid in the funnel decreasing at this instant.
Basically, I did
dh/dt = dh/dV * dV/dt
work out dh/dV and use the dV/dt given but kept getting the wrong answer.
Where did I go wrong?

Thanks

Hi
I am stuck on one question in an OCR C3 textbook.
Exercise 9B, Q7
A funnel has a circular top of diameter 20cm and height 30cm.
When the depth of the liquid in the funnel is 15cm, the liquid is dripping from the funnel at the rate of 0.2 cm^3 per second. at what rate is the depth of the liquid in the funnel decreasing at this instant.
Basically, I did
dh/dt = dh/dV * dV/dt
work out dh/dV and use the dV/dt given but kept getting the wrong answer.
Where did I go wrong?

Thanks