$A$ rhombus-shaped sheet with a perimeter of $40 \, cm$ and one diagonal of $12 \, cm$ is printed on both sides at the rate of $Rs. \, 5$ per $cm^2$. Find the total cost of printing.

$A$ rectangular plot is given for constructing a house, having a measurement of $40 \, m$ long and $15 \, m$ in the front. According to the laws, a minimum of $3 \, m$ wide space should be left in the front and back each, and $2 \, m$ wide space on each of the other sides. Find the largest area where the house can be constructed (in $m^2$).

The area of an equilateral triangle with each side measuring $16\,cm$ is how many times the area of an equilateral triangle with each side measuring $8\,cm$?

If $a, b, c$ are the lengths of three sides of a triangle,then the semiperimeter $(s)$ of the triangle is ..........

$A$ field is in the shape of a trapezium having parallel sides $90 \, m$ and $30 \, m$. These sides meet the third side at right angles. The length of the fourth side is $100 \, m$. If it costs $\operatorname{Rs} 4$ to plough $1 \, m^2$ of the field,find the total cost of ploughing the field (in $\operatorname{Rs}$).

According to Heron's formula,the area of a triangle $=$ ...........