Correct Answer - Option 2 : 21.3 cm
Concept:
Relationship between sleeper spacing, width of sleeper, and depth of ballast cushion is given by the following formula:
Sleeper Spacing = Width of Sleeper + (2 × Depth of Ballast Cushion)
Calculation:
Given Data:
Let D = depth of ballast cushion
Sleeper Spacing = 68 cm
Width of sleeper = 25.4 cm
Putting these data in above equation, we get,
68 = 25.4 + (2 × D)
So,
Depth of Ballast Cushion, \(D = \frac{{68 - 25.4}}{2} = 21.3\;cm\)