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The length of the minute hand of a wall clock is $21$ cm. Find the area swept by the minute hand in $45$ minutes.
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Sol. Angle swept by minute hand in $45$ minutes = $270^{\circ}$
Length of minute hand ($r$) = $21$ cm
$\therefore$ Area swept = $\frac{270}{360} \times \frac{22}{7} \times 21 \times 21$
= $1039.5$
Therefore, area swept by the minute hand in $45$ minutes is $1039.5 \text{ cm}^2$.
Length of minute hand ($r$) = $21$ cm
$\therefore$ Area swept = $\frac{270}{360} \times \frac{22}{7} \times 21 \times 21$
= $1039.5$
Therefore, area swept by the minute hand in $45$ minutes is $1039.5 \text{ cm}^2$.