North Carolina General Contractors Practice Exam

Which of the following methods checks the squareness of a concrete slab?

1. Using a level

2. Measuring the diagonals for equal length

3. Counting the number of tiles

4. Checking the corners for straights

The correct answer is: Measuring the diagonals for equal length

Measuring the diagonals for equal length is a widely accepted method for checking the squareness of a concrete slab because it relies on the properties of a right triangle. In a perfectly square corner, the two diagonals of a rectangle (or square) will be of equal length. By measuring the diagonal distances from one corner of the slab to the opposite corner, if the lengths are identical, it indicates that the corners are at right angles, confirming the squareness of the slab. This method is particularly effective as it provides a straightforward measurement that directly relates to the geometric definition of a square. If the diagonals are not equal, this suggests that the angles are not all exactly 90 degrees, indicating a potential issue with squareness.