f5 rate of change

1.A cone of height 2r cm and base radius r cm.The base radius increases at a oconstant rate of 0.1m/s.When the base radius is 6cm.Find the rate of change of the curved surface area of the cone with respect to time.

2.A circle with centre O and radius 3cm.P is movable point on the circumference of the circle and PQ is a rod of length 3cm.As P moves around the circle int the anti-cloclwise direction,Q slides along a horizontal rail through O.Let angle POQ=X and 0<X<π/2.If OP rotataes at a speed π/15 rad/s,find the rate of change of the area of triangle OPQ with respect to time when X=π/6.

3.A cross-section of a trough in the shape of triangular prism.The cross-section of the trough is an equilateral triangle of side 20cm adn the length of the trough is 40cm.
a)find the height and the area of triangle ABC
b)If water is poured into the trough at a constant rate of 10cm^3/min,find the rate of change of the depth of water with respect to time when the depth of water is 5cm.

有埋步驟啊吾該^^