Locomotive boiler tube count (standard textbook design): Identify the correct combination of the number of fire tubes and superheater tubes provided in a typical locomotive boiler.

Introduction / Context:
Locomotive boilers are multi-tubular fire-tube boilers designed for high evaporative capacity under variable load. Textbook examples frequently cite a canonical tube count pairing of fire tubes and superheater elements. This question checks recall of that standard combination used in many academic problems.

Given Data / Assumptions:

• Conventional locomotive boiler with firebox, large number of small fire tubes, and superheater elements.
• Counts refer to textbook standard (not every historical variant).
• Purpose: recognition, not design derivation.

Concept / Approach:
The cited “typical” configuration used in many exam references lists 157 small-diameter fire tubes that carry hot gases and 24 superheater elements (tubes) for raising steam temperature beyond saturation. While actual locomotives varied, this pairing is widely taught and expected in objective questions.

Step-by-Step Solution:
Recall standard numbers from boiler classifications.Cross-check with common alternatives; only one option matches the widely quoted pair.Select: 157 fire tubes and 24 superheated tubes.Confirm reasonableness: multi-tubular design needs many small tubes; superheater count is smaller.

Verification / Alternative check:
Illustrated locomotive boiler schematics in textbooks show large fire-tube bundles with a smaller set of superheater return bends approximating this count.

Why Other Options Are Wrong:
Other number pairs do not correspond to the commonly taught standard set and may mislead memory by near-values.

Common Pitfalls:
Assuming all locomotives share identical counts; question targets the textbook “typical” numbers, not every historical build.

Final Answer:
157 fire tubes and 24 superheated tubes