related rates problems. I do not remember how to do them so if you could please explain how you got an answer that would be much appreciated

problem 1:
The radius of a circle is increasing at a nonzero rate, and at a certain instant, the rate of increase in the are of the circle is numerically equal to the rate of increase in its circumference. at this instant, the radius of the circle is?

problem 2:
The diameter and height of a paper cup in the shape of a cone are both 4 inches. water is leaking out at a rate of 1/2 cubic inch per second. Find the rate at which the water level is dropping when the diameter of the surface is 2 inches.

problem 3:
A railroad track and a road cross at right angles. An observer stands on the road 70 meters south of the crossing and watches an eastbound train traveling at 60meters per second. At how many meters per second is the train moving away from the observer 4 seconds after it passes the intersection?

problem 4:
A family standing on the ground is watching a jet approach. The jet is approaching at a rate of 12 miles per minute at an altitude of 8 miles.
a) At what rate is the straight-line distance between the family and the jet changing when the jet is 16 miles from the family?

b) At what rate (in radians per minute) is the angle of altitude changing when the straight-line distance from the jet to the family is 36 miles?

please help me with these problems. my AP exam is coming up in a few weeks and I don't remember how to do this stuff.

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