The sum of all interior angles of a regular polygon is twice the sum of all its exterior angles.  The number of sides of the polygon is

The area of a circle is proportional to the square of its radius. A small circle of radius 3 cm is drawn within a larger circle of radius 5 cm. Find the ratio of the difference between the area of the larger circle and that of the smaller circle to the area of the larger circle.

The maximum number of common tangents drawn to two circles when both the circles touch each other externally is 

Find the area of the largest triangle made in a semicircle of r cm radius?

In △ABC, M and N are the points on side BC such that AM ⊥ BC, AN is the bisector of ∠A, and M lies between B and N. If ∠B = 68°, and ∠C=26°, then the measure of ∠MAN is:

In ΔABC, ∠C=90° and CD is perpendicular to AB at D. If AD/BD=$$ {\sqrt{k}}$$, then AC/BC=?

In any triangle ABC, AB + BC = 12 cm, BC + CA = 14 cm and CA + AB = 18 cm. What will be length of radius of a circle, if the perimeter of circle is equal to the perimeter of triangle ABC? 

ABCD is a trapezium in which AB is parallel to CD and AB = 4 ( CD ) . The diagonals of the trapezium intersects at O. what is the ratio of area of triangle DCO to the area of the triangle ABO ?