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?

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

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

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

Final Answer1.26