In the first problem, I am worried you may have rounded too imprecisely, especially in the second line. Also, you want the time taken for the height to go from 0 to 0.8, so you can use a definite integral.

In the second problem, your description has a cone of radius 0.06m while the diagram has diameter 0.06m. Also, I'm not sure where the factor of 0.6 came from in the speed of water leaving the hole.