The length of a rectangle is increased by $60 \%$. By what percent would the width have to be decreased so as to maintain the same area?

$A$ man runs around a circle of $50\, m$ radius at a speed of $12\, km/h$. Find the time taken by him for going around it ten times (in $minutes$).

$ABC$ is a triangle. $AB = 5 \text{ cm}$,$AC = \sqrt{41} \text{ cm}$,and $BC = 8 \text{ cm}$. $AD$ is perpendicular to $BC$. What is the area (in $\text{cm}^2$) of triangle $ABD$?

$A$ ladder is placed so as to reach a window $63 \ cm$ high. The ladder is then turned over to the opposite side of the street and is found to reach a point $56 \ cm$ high. If the ladder is $65 \ cm$ long,then the width of the street is........$cm$

If the perimeter of an equilateral triangle is $12\, m$,then find its area.

In the given figure,$OP = PQ = 14 \, cm$ and semicircles are drawn on $OP$,$PQ$,and $OQ$ as diameters. Then,the perimeter of the shaded area is . . . . . . $cm$.