How much water should be filled in a container 21 cm in height, so that it appears half filled when viewed from the top of the container? (Refractive index of water = 4 3) 8 cm 10.5 cm 12 cm 14 cm

It is given that, Radius of a circle = 21 cm. We know that π = 22 / 7, So the circumference of a circle = 2 π r Substituting the values, = 2 ∗ 22 / 7 ∗ 21 So we get, = 2 ∗ 22 ∗ 3 = 132 cm.

In a circle of radius 21 cm, an arc subtends an angle of 60∘ at the centre. Find : (i) the length of the arc (ii) area of the sector formed by the arc.

Find the surface area of a sphere, if its diameter is 21 c m.

In a circle of radius 21 cm, an arc subtends an angle of 60 at the center. Find: (i) the length of the arc (ii) area of the sector formed by the arc (iii) Area of the segment formed by the corresponding chord

In a circle of radius 21 cm, an arc subtends an angle of 60∘ at the centre. Find : (i) the length of the arc (ii) area of the sector formed by the arc.

The volume of two spheres are in the ratio 64 : 27 . Find the radiii if the sum of the radii is 21 cm.

Find the angle in radian through which a pendulum swings if its length is 75 and the tip describes an arc of length 21 cm .

Given that, Volume of two sphere are in ratio = 64: 27 We know that , Volume of sphere = 4 3πr3 Then, V olumeof sphere(1) V olumeof sphere (2)= 64 27 4 3πr13 4 3πr23 = 64 27 r13 r23 = 64 27 r1 r2 = 4 3 Then, Ratio of areas both spheres areaof sphere (1) areaof sphere (2) = 4πr12 4πr22 = r12 r22 = (r1 r2)2 = (4 3)2 = 16 9 Hence, this is the answer.

Water is flowing at the rate of 15 km per hour through a pipe of diameter 14 cm into a rectangular tank which is 50 m long and 44 m wide. Find the time in which the level of water in the tank will rise by 21 cm.