Exercise 5.4.28. For each of the following sets of numbers, determine which of the four group properties holds, using the operation of multiplication. It a property does not hold, give a specific counterexample which shows that the property is false. State also whether or not each set is a group. (a) Integers; (b)Positive integers; (c) Rational numbers; (d) Real numbers; (e) Complex numbers.

A tree casts a shadow 14 feet long. A flagpole that is 20 feet tall casts a shadow 8 feet long. The triangle formed by the tree and its shadow is similar to the triangle formed by the flagpole and its shadow. Verify that the tree is 35 feet tall.

A sumbarine is positioned at 300 feet below sea level. A bird is flying 100 feet above sea level. How many feet above the sumbarine is the bird?

a home cast an 85-foot shadow. At the same time. a bush casts a 10-foot shadow. if the bush is 6 feet tall, how tall is the house.