Practice | Hashtable

1. The diameter of a spare is 8 cm. It is melted and drawn into a wire of diameter 3 mm. The length of the wire is :

A. 36.9 m

B. 37.9 m

C. 38.9 m

D. 39.9 m

Solution:

Let the length of the wire be h
Then,

\begin{aligned} π \times \frac{3}{20} \times \frac{3}{20} \times h = \frac{4}{3} π \times 4 \times 4 \times 4 \\ \Rightarrow h = (\frac{4 \times 4 \times 4 \times 4 \times 20 \times 20}{3 \times 3 \times 3}) c m \\ \Rightarrow h = (\frac{102400}{27}) c m \\ \Rightarrow h = 3792.5 c m \\ \Rightarrow h = 37.9 m \end{aligned}

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