Height of an equilateral triangle is $6 \, cm$. Find its side? (in $cm$)

$2$ small circular parks of diameters $16 \ m$ and $12 \ m$ are to be replaced by a bigger circular park. What would be the radius of this new park,if the new park occupies the same space as the two small parks?

$A$ wire bent in the form of a circle of radius $42 \, cm$ is bent in the form of a rectangle whose sides are in the ratio of $6:5$. The smaller side of the rectangle is (in $cm$)

The length of a rectangle is twice its breadth. If its length is decreased by $5\, cm$ and breadth is increased by $5\, cm$,the area of the rectangle is increased by $75\, cm^2$. Then the length of the rectangle is......$cm$.

In $\triangle ABC$,$\angle A = 90^{\circ}$ and $AD \perp BC$,where $D$ lies on $BC$. If $BC = 8 \ cm$ and $AC = 6 \ cm$,then the ratio of the area of $\triangle ABC$ to the area of $\triangle ACD$ is:

In the given figure,$y$ is both the radius of the larger circle and the diameter of the smaller circle. Find the area of the shaded region.