The area of a triangle is one-half the product of its base and height. In a right triangle, the base and height are perpendicular, so this formula applies directly. Multiply 9 by 12 to get 108, then take half to get 54. So the area is 54 square inches. The other numbers would come from either forgetting to divide by two or using different dimensions, but with the given base and height, 54 is the correct result.

Lockout/tagout protects workers by preventing the machine from energizing or releasing stored energy while maintenance is being performed. Before work begins, all energy sources—electrical, hydraulic, pneumatic, mechanical, thermal, gravity, and stored energy—are shut down and isolated. A lock is placed on the energy-isolating device to physically prevent re-energizing, and a tag warns that service is in progress and indicates who is responsible. Only the person who applied the lock should remove it, after work is complete and verification shows zero energy. This approach directly stops unexpected startup or the sudden release of energy that could injure someone, which is why it’s the core purpose of lockout/tagout. While it also helps reduce risks like electric shock or fire hazards, those are potential outcomes, not the primary mechanism. Noise exposure isn’t addressed by lockout/tagout.

In technical drawings, different line types convey what you can and can’t see in a given view. The line type used for edges that aren’t visible in the current view is the hidden line, drawn as a series of short dashes. This convention lets you understand features that exist but are obscured by other parts of the object. Visible edges are shown with solid lines, center lines denote symmetry or axes, and dimension arrows indicate measurements. So, for edges not visible in the current view, the appropriate line type is the hidden line.

Dry powder extinguishers are a versatile type that can handle three common fire classes: ordinary combustibles, flammable liquids, and energized electrical equipment. They work by coating the fuel, interrupting the chemical reactions occurring in the flame, and forming a crust that helps prevent reignition. Because they are rated for all three classes, the best answer is the one that indicates coverage of all three categories. If you thought it only applied to one or two classes, you’d miss the extinguisher’s broad rating. One practical note: the powder leaves a residue that can be difficult to clean and may affect sensitive electronics, so consider the context when choosing an extinguisher.