How much of the total length of a ladder is considered its working length at a 70-degree angle?

The concept of working length refers to the effective portion of the ladder that can be used to reach a target area when the ladder is positioned at a specific angle. At a 70-degree angle, the working length is calculated based on the cosine of the angle. The cosine of 70 degrees is approximately 0.34, which indicates how much of the total length of the ladder is effective when used at that angle.

To find the working length at a 70-degree angle, you multiply the total length of the ladder by the cosine of 70 degrees. In this calculation, it turns out that approximately 94% of the total length is considered effective for use at this angle, which aligns with the correct answer. This means that the majority of the ladder's length can be safely and effectively utilized when set up at 70 degrees, making it a critical factor for fire officers to understand when deploying ladders in various situations. The remaining percentage reflects the length of the ladder that would be less useful or unable to reach designated targets when positioned at that angle.