The total piston displacement for the 4-cylinder engine described earlier is approximately

• A. 180
• B. 250
• C. 200
• D. 300

Answer: (C)

Engine displacement is the total volume the pistons sweep as they move from bottom dead center to top dead center. For each cylinder, displacement equals pi times the bore divided by 2 squared, multiplied by the stroke (that is, V = π × (bore/2)² × stroke, or equivalently (π/4) × bore² × stroke). The engine’s total displacement is the sum of all cylinders’ swept volumes, so for four cylinders it’s four times the per‑cylinder displacement (which can also be written as π × bore² × stroke).

If the described engine yields about 50 units of volume per cylinder, multiplying by four gives roughly 200 units in total. That’s why the approximate total displacement is 200 in the units used in the description. The other values would require per-cylinder volumes quite different from what the bore and stroke provide.