64 small solid iron spheres of radius 'r' are melted to form a big sphere of radius R. If S and S' are surface areas of the small and the big sphere respectively, then find the ratio S' : S.

A sector as shown in the figure is assembled to form a cone. What is the base radius (in cm) of the cone so formed ? $\left(\pi = \frac{22}{7}\right)$

A right circular metal cone (solid) is 42 cm high and its radius is $\frac{21}{2}$ cm. It is melted and recast into a sphere. Then the radius of the sphere will be:

$V_1, V_2, V_3$ and $V_4$ are the volumes of four cubes of side lengths x cm, 2x cm, 3x cm and 4x cm respectively. The following statements regarding these volumes are given below.

(A) $V_1 + V_2 + 2V_3 < V_4$

(B) $V_1 + 3V_2 > V_3 + V_4$

(C) $2(V_1 + V_3) + V_2 = V_4$

(D) $V_1 + 4V_2 + V_3 < V_4$

Which of these statements is/are correct?

Choose the correct answer from the options given below:

A right angle triangle is rotated along the base. If the perpendicular, hypotenuse and base of the triangle are 8 cm, 10 cm and 6 cm respectively. Find the volume of the cone formed through rotation. ($\pi = 3.14$)

Consider the surface area of the following solids.

A. A cube of edge 4 cm.

B. A cylinder with a diameter of base 14 cm and height 35 cm.

C. A hemisphere with 28 cm diameter.

D. A sphere with a radius of 7 cm.

Arrange the above in decreasing order and choose the correct answer from the options given below:

Consider the surface area of the following solids.

A. A cube of edge 9 cm.

B. A cuboid of edges 18 cm, 14 cm and 7 cm.

C. A cylinder with radius of 14 cm and height 80 cm.

D. A sphere with radius of 14 cm.

Arrange the above in decreasing order.