If the radius of a sphere is doubled,then its surface area is increased by (in $\%$)

The length of canvas $75 \, cm$ wide required to build a conical tent of height $14 \, m$ and the floor area $346.5 \, m^{2}$ is.........$m$

$A$ rectangular plot,$36 \, m$ long and $28 \, m$ broad,has two concrete roads $5 \, m$ wide running in the middle of the park,one parallel to the length and the other parallel to the breadth. What would be the total cost of gravelling the plot,excluding the area covered by the roads,at ₹ $3.60$ per $m^{2}$? (in $Rs.$)

If each edge of a cube is increased by $50 \%$,the percentage increase in its surface area is (in $\%$)

$A$ cone of height $9 \, cm$ with diameter of its base $18 \, cm$ is carved out from a wooden solid sphere of radius $9 \, cm$. The percentage of the wood wasted is

$A$ cylinder with base radius of $8\, cm$ and height of $2\, cm$ is melted to form a cone of height $6\, cm.$ The radius of the cone will be (in $cm$):