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Preferred numbers (Renard series): constant factor for the R10 series In engineering standardization, the Renard R10 series uses a constant ratio between successive preferred numbers. What is the constant factor (common ratio) for the R10 series?

Difficulty: Easy

1.06
1.12
1.26
1.58

Correct Answer: 1.26

Explanation:

Concept
The Renard R5/R10/R20 series are geometric progressions. For R10, the common ratio is the tenth root of 10.

Step-by-step
Common ratio, r = 10^(1/10)r ≈ 10^0.1 ≈ 1.2589 ≈ 1.26

Common pitfall
Confusing R10 with R5 (ratio ≈ 1.58) or R20 (ratio ≈ 1.12).

Final Answer
1.26

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