Quick questions on Related rates of change: linking changing quantities via implicit differentiation

The cone is where most students go wrong, so it is worth slowing down. The cone-volume formula $V = \frac{1}{3}\pi r^2 h$ has two changing lengths, $r$ and $h$. If you differentiate it as it stands you get a $\frac{dr}{dt}$ term you were never given and cannot find. The fix is to notice that the water surface and the cone wall always form similar triangles, so $r$ and $h$ stay in a fixed ratio.

If the question says "approaching", the rate is negative when you define distance as positive away. State the direction explicitly in words.

A rate has units like m/s or cm$^3$/s. Final answers without units are incomplete.