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A minute hand of a clock is 20cm long.How far does the tip of the hand move in 20 minutes.

$(a)\;\large\frac{20\pi}{3}$$\qquad(b)\;\large\frac{10\pi}{3}$$\qquad(c)\;\large\frac{40\pi}{3}$$\qquad(d)\;None\;of\;these$

1 Answer

The minute hand moves through $120^{\large\circ}$ in 20 minutes or moves through $\large\frac{2\pi}{3}$ radians.
Given :
Length of the minute hand is 20cm.
Distance moved by the tip of the hand=$l$
$l=r\theta$
$\Rightarrow l=20\times \large\frac{2\pi}{3}$
$\Rightarrow \large\frac{40\pi}{3}$cm
Hence (c) is the correct answer.
answered Oct 9, 2013 by sreemathi.v
 
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