Volumes, Areas, Ratios and Proportions

See the attached file.
38. if the circumference of a great circle of the Earth is about 40,000 km. The atmosphere of the Earth has an altitude of about 550 km. Find the volume of the Earth and its atmosphere.

39. A steel gas tank has the shape of a sphere. A radius of the inner surface of the tank is 2 feet long. The tank itself is made of 1/4 inch thick steel. Find the difference between the outside area and inside area of the tank.

40. If a gallon of paint will cover 400 square feet, how many gallons of paint will be needed to paint both the inside and the outside of the tank in the above problem.

The next problems go with the attachment. There are 3 problems

24.Use the scales of miles and the map above to estimate the number of square miles contained in the wildlife refuge. If there are 640 acres in 1 square mile, how many acres does the refuge contain? Describe your method for estimating the area of the refuge.

25. Animal overpopulation within the refuge must be monitored in order to prevent diseases and environmental damage. A deer census reveals that there are an average of 3 deer on every 20 acres of the refuge. Give an estimate for the number of deer that live in the wildlife refuge.

26. Most of the endangered whooping cranes spend their summers in Canada and their winters in or near the Arkansas National Wildlife Refuge. If there are 123 whooping cranes alive in the wild and 98 of them are spotted inside the wildlife refuge, what percentage of the whooping crane population is inside the refuge?

27. Marine Biology In a marine environment, 1 pound of sea water consists of 6.5% minerals and organic material. How many pounds of pure water are there in 57 pounds of sea water?