tolong bantu kaka cara kerjainya gimana?? makasih..☺

[tex]Va = Vc \\ Wa \times Ra= Wc \times Rc \\ \frac{Wa}{Wc} = \frac{Rc}{Ra} \\ \frac{Wa}{Wc} = \frac{30}{15} \\ \\ Wb = Wc \\ Wb = 15 \\ \\ Wb : Wa = 15 : 30 = 1 : 2[/tex]

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Jadi, jawabannya D (1 : 2)