CALCULATION: A trench 5 feet deep and 100 feet long requires a means of egress so no worker travels more than 25 feet of lateral distance to reach a ladder. What is the MINIMUM number of ladders needed, spaced so every point is within that distance?

Explanation

Correct: with a 25-ft maximum lateral travel, one ladder covers 25 ft to its left and 25 ft to its right, i.e., a 50-ft span. A 100-ft trench therefore needs 100 / 50 = 2 ladders, positioned so their coverage zones span the length. One ladder covers only 50 ft (leaving the ends beyond 25 ft); 4 or 5 ladders exceed the minimum required.