A cylindrical ice pillar is melting in a laboratory. At time ttt minutes, the pillar has a radius r mmr\text{ mm}r mm and a length L=8r mmL = 8r\text{ mm}L=8r mm.
The cross-sectional area of the pillar, AAA, is decreasing at a constant rate of 1.2 mm2 min−11.2\text{ mm}^2\text{ min}^{-1}1.2 mm2 min−1.
Find the value of drdt\frac{dr}{dt}dtdr when r=3r = 3r=3.
Determine the rate of decrease of the volume of the pillar when r=5r = 5r=5.
Practise Edexcel A Level Maths 9.10 Rates of Change with exam-style questions for A Level Maths. 24 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.