Problem:
The perimeter of a rhombus is and each of the two acute angles measures . What is the volume of the solid obtained by rotating the rhombus about one of its sides?
Problem:
The perimeter of a rhombus is and each of the two acute angles measures . What is the volume of the solid obtained by rotating the rhombus about one of its sides?
Pick one
Solution:
The answer is (B). We observe that the solid of revolution obtained by rotating a rhombus about one of its sides can be seen as a cone superimposed on a "hollowed-out" cylinder. The region of space that is hollowed out of the cylinder is equal to the cone above it, consequently the required volume is equivalent to the volume of a cylinder having as height the side of the rhombus and as radius the height of the rhombus (half the side, that is ). The calculation then gives