A ladder must be able to support how many times the weight of the expected load?

The requirement for a ladder to support three times its expected load is based on safety factors employed in engineering and construction. The rationale behind this guideline is to ensure that the ladder has sufficient strength and stability to safely support not only the intended load but also any dynamic forces that may occur while in use, such as movement, shifting weight, or potential impacts.

Using a safety factor of 3.3 times the expected load means that if the maximum load anticipated is 100 pounds, the ladder should be rated to handle up to about 330 pounds. This level of safety margin helps to accommodate variations in materials, potential wear and tear, and unexpected conditions, significantly reducing the risk of failure and accidents.

In summary, the requirement for a ladder to support 3.3 times the expected load is established to ensure safety and performance under varying conditions, making it the appropriate choice for this question.