Final answer:
The cross-sectional area of the marble column with dimensions 140 mm by 180 mm is calculated as 25,200 mm² by multiplying the length by the width.
Step-by-step explanation:
To calculate the cross-sectional area of a marble column with dimensions 140 mm by 180 mm, you multiply the two dimensions together as follows:
Area = length × width
In this case:
Area = 140 mm × 180 mm = 25,200 mm²
Therefore, the cross-sectional area of the marble column is 25,200 mm².