Washer

The washing machine drum washes at 71 RPM. The washing machine motor pulley has a diameter of 8 cm. What must be the diameter of the drum machine pulley when the motor is at 351 RPM?

Correct answer:

D =  39.5 cm

Step-by-step explanation:

$$\begin{gathered} n_1=71 \\ {n}_2=351 \\ d=8\text{cm} \\ {s}_1=s_2 \\ {n}_1\cdot D=n_2\cdot D \\ D=\frac{n_2}{n_1}\cdot d=\frac{351}{71}\cdot 8=\frac{351\cdot 8}{71}=\frac{2808}{71}=\frac{2808}{71}\text{cm}=39.5\text{cm} \end{gathered}$$

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