A solid sphere of diameter 7 cm is cut into two equal halves. What will be the increase (in cm.²) in the total surface area?

If each interior angle is doubled of each exterior angle of a regular polygon with n sides, then the value of n is 

A sector area of 4%   is removed from a circular sheet of paper of diameter 50 cm, If the remaining part is used to make a conical surface , then the ratio of radius and height of the-

A container in the shape of a frustum of a cone having diameters of its two circular faces as 35 cm. and 30 cm and vertical height 14 cm. is completely filled with oil. If each cm3 of oil has mass 1.2g, then find the cost of oil in the container if its costs Rs. 40 per kg.

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?

Inside a square PQRS, ΔQTR is an equilateral triangle. If RT and QS intersect at O, then ∠QOR is equal to-

If each side of a cube is increased by 10%. Then find the percent change in the volume of the cube.

If the numerical value of the perimeter of an equilateral triangle is √3 times the area of it, then the length of each side of the triangle is: