Lesson Objectives. 1  List the main features of the seafloor: mid-ocean ridges, deep sea trenches, and abyssal plains. 2  Describe what seafloor magnetism tells scientists about the seafloor. 3  Describe the process of seafloor spreading.
Assignment Help. The average diameter of sand dollars on a certain island is 4.50 centimeters with a standard deviation of 1.00 centimeters. If 9 sand dollars are chosen at random for a collection, find the probability that the average diameter of those sand dollars is more than 4.13 centimeters.he average diameter of sand dollars on a certain island is 4.50 centimeters with a standard deviation of 1.00 centimeters.
The sand dollarâs test, or skeleton, is round and disc-like, and is covered with deep reddish-purple spines. The sand dollar loses its purple color when it is washed ashore. As with other sand dollars, the common sand dollar has five petal-like furrows or pores on its test. These are used to move sea water into its internal water-vascular system, which allows for movement.