Construct the right triangle $PQR$ whose perpendicular sides are $4.5 \mathrm{cm}$ and $6 \mathrm{cm}$. Also locate its circumcentre and draw the circumcircle.

In the quadrilateral $ABCD, AB=BC$ and $AD=DC$. Measure of $\angle BCD$ is

$ABCD$ is a square, diagonals $AC$ and $BD$ meet at $O$. The number of pairs of congruent triangles with vertex $O$ are

In the given figure $CE\parallel DB$ then the value of $x°$ is

In the figure, $O$ is the centre of the circle and $\angle ACB=40°$ then $\angle AOB=$