When taking four readings around 360 degrees, the vertical readings should equal which of the following?

When taking four readings around 360 degrees, the vertical readings should be equal to both the horizontal readings and the readings taken at 3 o'clock and 9 o'clock positions. This principle derives from the basic understanding of how level measurements should maintain consistency in a balanced system.

Vertical readings indicate the vertical alignment of the machine or structure, while horizontal readings (often taken at 3 and 9 o'clock) reflect the level condition in the horizontal plane. For a properly aligned system, the vertical readings should match the average of the horizontal measurements accounted for.

Taking both the horizontal readings and the specific 3 o'clock and 9 o'clock readings into consideration ensures that the system is correctly aligned in both directions. This adherence to the principle of balance is crucial in millwright practices, where precise alignment is necessary for the efficiency and longevity of mechanical systems. Therefore, the option that includes both conditions reflects a comprehensive understanding of leveling and alignment in the field.