倍率
ばいりつ · bairitsu · JLPT N1 · noun
magnification
倍 — person radical 亻 + 咅 (phonetic)
倍 is a semantic-phonetic compound: the person radical 亻 hints at the meaning, while 咅 supplies the sound 'bèi'. The original sense was 'to turn one's back on' or 'double back', which shifted to today's core meaning of 'times' or 'fold' in multiplication (e.g. 三倍 = threefold).
率 — twisted silk threads with droplets, plus 十
率 originally pictured a net or twisted bundle of silk cords with water droplets shaking off, suggesting something being led or pulled along. From 'leading a rope' it extended to 'lead, command' (shuài) and to 'rate, ratio' (lǜ), as in a fixed proportion. The two readings share this core image of a guiding measure.