Hi, I'm new here and I would be very grateful if you guys can help me with these 2 exercises :-)

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1. A container in the shape of a right circular cone of heighr 20 cm and radius 5cm is held vertex downward and filled with water which then drips out from the vertex at the rate of 5cm^{3}/s. Find the rate of change of the height of water in the cone when it is half empty (measured by volume) <= not quite sure here why the change of height is measured by volume, but this one I take from 'The core course for A-level', so it's rather confusing.

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2. A 5m ladder is held against the wall. The top of the ladder is sliding down the wall at the rate of 1m/s. Find the rate af change of the angle between the ladder and the ground when the vertical distance between the top of the ladder and the foot of the wall is 3m.

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I know how this type of exercise is normally solved, but I just fail to apply it into these 2