Geometry questions require properties and given information, rather than an estimate from the picture. Label what is known and what must be found. Separate a length, an area and a volume before selecting a formula; they describe different quantities and carry different units.
Reason through the task
Draw or annotate the relevant triangle, circle or solid. Mark right angles only when supplied or logically established. Identify which facts justify the relationship: parallel lines, similar triangles, a radius or a perpendicular height. Keep an expression exact until comparison with the options. If a diagram is not stated to scale, its appearance supplies no extra equality or angle measurement. Use the drawing to organize known facts, not to manufacture new ones.
Worked example and a tempting error
Original example: a right triangle has legs six and eight. Its hypotenuse satisfies c² = 6² + 8² = 100, so c = 10. Its area is one-half times six times eight, or twenty-four square units. Adding the legs to get fourteen confuses a boundary sum with diagonal length. Calling the area forty-eight forgets that the right triangle occupies half of the corresponding rectangle. Each result follows a different geometric relationship.
Try a different case
Transfer: a circle has diameter ten centimeters. Its radius is five, so area is π(5²) = 25π square centimeters and circumference is 2π(5) = 10π centimeters. Using ten as the radius makes the area four times too large. State the radius before substitution and retain the units; that pair of checks catches both the diameter error and an area-versus-circumference mix-up.