The area of the incircle of an equilateral triangle of side $42 \ cm$ is (in $cm^2$)

$A$ circular wire of diameter $112 \, cm$ is cut and bent in the form of a rectangle whose sides are in the ratio of $9:7$. The small side of the rectangle is......$cm$.

The area of a ring whose outer and inner radii are respectively $20 \, cm$ and $15 \, cm$ is? (in $cm^2$)

$A$ rectangular farm has to be fenced on one long side, one short side, and the diagonal. If the cost of fencing is ₹ $10$ per $m$, the area of the farm is $1200 \ m^2$, and the short side is $30 \ m$ long, how much would the job cost? (in ₹)

The smallest side of a right-angled triangle is $8\, cm$ less than the side of a square of perimeter $56\, cm$. The second largest side of the right-angled triangle is $4\, cm$ less than the length of the rectangle of area $96\, cm^2$ and breadth $8\, cm$. What is the largest side of the right-angled triangle? (in $cm$)

$A$ room is $7 \text{ m}$ long and $5 \text{ m}$ broad. The doors and windows occupy $5 \text{ m}^2$. The cost of papering the remaining part of the walls with paper $75 \text{ cm}$ wide,at ₹ $4.20$ per piece of $13 \text{ m}$,is ₹ $39.20$. Find the height of the room (in $\text{m}$).