In a polygon, the sum of the interior angles is double the sum of the exterior angles. What is the number of sides of the polygon?

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? 

If there are four lines in a plane, then what cannot be the number of points of intersection of these lines? 

In ΔABC, AB=c cm, AC= b cm and CB=a cm, If  ∠A=2 ∠B, then which of the following is true?

If the circumradius of an equilateral triangle ABC is 8 cm, then what is the height of the triangle?

If the area of a circle is 9π sq.cm then it circumference is

Which cities were India's first steel project-

AB is diameter of a circle with centre 'O'. CD is a chord which is equal to the radius of the circle. AC and BD are extended so that they intersect each other at point P. Then find the value of ∠ APB.