The length of a long wall in the long and short wall method of estimation is centre to centre distance between the walls and
- Awidth of the wall
- Bhalf of its width on each sideCorrect
- Cone-fourth width of wall on each side
- Done-third width of wall on each side
Solution
Concept
Long wall is measured out-to-out, short wall is measured in-to-in.
Formula
Long wall length = c/c length + half width on each side = c/c length + width; Short wall length = c/c length - width
Step-by-step solution
1. In this method, long walls are taken out-to-out. 2. Out-to-out length = centre to centre length + half width on one side + half width on other side. 3. So we add half of the wall width on each side.
Explanation
In the long wall and short wall method, long walls are measured from outer face to outer face. So we add half the wall width at each end to the centre line length. Short walls are measured in-to-in, so half width is subtracted at each end.
Why the other options are wrong
A: Adding the full width at one end is not how the rule is stated. C: One-fourth width on each side is not used. D: One-third width on each side is not used.
Shortcut
Long wall = c/c + width (out-to-out); Short wall = c/c - width (in-to-in).
Common mistake
Mixing up the long wall rule (add) with the short wall rule (subtract).
Correct answer: B) half of its width on each side