At clock times 12, 18, 24 and 30 sec, we observe water depths of 44.6, 41.2, 39.2 and 38.8 cm.

• At what average rate does the depth change during each time interval?

Sketch a graph of depth vs. clock time.

• Use a sketch to explain why the slope of this graph between 12 and 18 sec represents the average rate at which depth changes during this time interval.

If f(x) = x², what are the vertex and the three basic points of the graphs of f(x- 1.25), f(x) - 1.85, .2 f(x) and .2 f(x- 1.25) + 1.85. Quickly sketch each graph.