rectangular parallelepiped

Problem 14
Find the angles that the diagonals of the rectangular parallelepiped 2 in. by 3 in. by 4 in. makes with the faces.
 

Problem 9
A solid concrete porch consists of 3 steps and a landing. The steps have a tread of 11 in., a rise of 7 in., and a length of 7 ft.; the landing is 6 ft. by 7 ft. How much material was used in its construction?
 

Problem 8
An electric refrigerator is built in a form of rectangular parallelepiped. The inside dimensions are 3 ft. by 2.6 ft. by 1.8 ft. A freezing unit (1.1 ft. by 0.8 ft. by 0.7 ft.) subtracts from the storage room of the box. Find the capacity of the refrigerator.
 

Problem 7
The edges of the trunk are 3 ft., 4 ft., 6 ft. A second trunk is twice as long; the other edges are 3 ft., 4 ft. How do their volumes compare?
 

Problem 6
A tank, open at the top, is made of sheet iron 1 in. thick. The internal dimensions of the tank are 4 ft. 8 in. long; 3 ft. 6 in. wide; 4 ft. 4 in. deep. Find the weight of the tank when empty and find the weight when full of salt water. (Salt water weighs 64 lb/ft³ and iron is 7.2 times as heavy as salt water.
 

Problem 5
How many cubic yard of material are needed for the foundation of barn 40 by 80 ft., if the foundation is 2 ft thick and 12 ft. high.
 

Problem 4
A packing box 2.2 ft. by 4.9 ft. by 5.5 ft. is to be completely covered with tin. How many square feet of the metal are needed? (Neglect waste for seams, etc.)