A quadrilateral has one diagonal of length 36 cm, and the perpendiculars from the other two vertices to this diagonal are 20 cm and 10 cm. What is the area of this quadrilateral?
540 cm2
The diagonal splits the quadrilateral into two triangles, each having the diagonal as its base.
The area of a quadrilateral in this form is \(\frac{1}{2}\times d\times(h_1+h_2)\), where \(d\) is the diagonal and \(h_1\), \(h_2\) are the perpendiculars from the two opposite vertices.
Here \(d=36\) cm, \(h_1=20\) cm and \(h_2=10\) cm.
Area \(=\frac{1}{2}\times36\times(20+10)=\frac{1}{2}\times36\times30\).
Area \(=18\times30=540\).
Hence, the area of the quadrilateral is 540 cm2.
The shorter side of a rectangle is 15 cm less than the longer side. The numerical value of its area is equal to 5 times the numerical value of its perimeter. What is the length (in cm) of its longer side?