$A$ tank is $25 \ m$ long,$12 \ m$ wide and $6 \ m$ deep. The cost of plastering its walls and bottom at $75 \ paise/m^2$ is (in $Rs.$)

$A$ man walked diagonally across a square plot. Approximately what was the percent saved by not walking along the edges?

$2$ 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?

$A$ hollow spherical shell is made of a metal of density $4.9 \, g/cm^3$. If its internal and external radii are $10 \, cm$ and $12 \, cm$ respectively,find the weight of the shell. (Take $\pi = 3.1416$) (in $gm$)

Three circles of radius $21 \, cm$ are placed in such a way that each circle touches the other two. What is the area of the portion enclosed by the three circles? (in $sq \cdot cm$)

The length of a rectangular field is twice its breadth. If the rent of the field at ₹ $3500$ per hectare is ₹ $28000$,then find the cost of surrounding it with a fence at ₹ $5$ per meter (in ₹).