What is the area of a triangle whose sides are $9\, cm$,$12\, cm$,and $15\, cm$? (in $cm^2$)

The ratio of the area of the incircle and circumcircle of a square is?

The area of a quadrilateral is $420 \, m^{2}$ and the perpendiculars drawn to one diagonal from the opposite vertices are $18 \, m$ and $12 \, m$. Then,the length of the diagonal is......$m$

Find the number of bricks,each measuring $25\, cm \times 12.5\, cm \times 7.5\, cm$,required to construct a wall $12\, m$ long,$5\, m$ high,and $0.25\, m$ thick,if the sand and cement mixture occupies $5\%$ of the total volume of the wall.

If the area of an equilateral triangle is equal to the area of an isosceles triangle whose base and equal sides are $16 \, cm$ and $10 \, cm$ respectively,then the side of the equilateral triangle is......$cm$

The diameters of two concentric circles are $8\, cm$ and $10\, cm$. The area of the region between them is