Definition of crusher reduction ratio:\nIn crusher terminology, the reduction ratio is best defined as which of the following?

Introduction / Context:
“Reduction ratio” provides a compact descriptor of how much a crusher reduces the size of the feed. It supports quick equipment comparisons and preliminary sizing. While exact definitions can use characteristic sizes (e.g., 80% passing F80/P80), the qualitative meaning remains the ratio of typical feed size to typical product size.

Given Data / Assumptions:

• Single crusher stage under steady operation.
• Characteristic sizes represent opening or 80% passing sizes.

Concept / Approach:
Reduction ratio R is commonly expressed as R = F/P, with F a characteristic feed dimension and P the corresponding product dimension. Primary crushers often have ratios around 3–8; secondary/tertiary units can be higher. The ratio is not a universal constant and does not by itself set absolute feed/product sizes; rather, it scales them.

Step-by-Step Solution:

Verification / Alternative check:
Equipment data sheets and design examples compute reduction ratio using 80% passing sizes or nominal openings, consistent with option (a).

Why Other Options Are Wrong:

• (b) Inverts the definition.
• (c) Mischaracterises R as a constant; R varies by machine and duty.
• (d) Contradicts the definition tied to feed/product sizes.
• (e) Invents an unrelated index.

Common Pitfalls:
Mixing “openings” with “P80/F80” values; be consistent about which characteristic sizes are used.

Final Answer:
Ratio of feed opening (or feed size) to discharge opening (or product size)