A hollow spherical metallic ball has an external diameter 6 cm and is 1/2 cm thick. The volume of metal used in the metal is:

Answer: Option B

Explanation:

In this type of question, first we will calculate the volume of water displaces then will multiply with the density of water.
Volume of water displaced = 3*2*0.01 = 0.06 m cube

Mass of Man = Volume of water displaced * Density of water

= 0.06 * 1000 = 60 kg

Answer: Option D

Explanation:

l = (48 - 16)m = 32 m, [because 8+8 = 16]
b = (36 -16)m = 20 m,
h = 8 m.

Volume of the box = (32 x 20 x 8) m cube
= 5120 m cube.

Answer: Option C

Explanation:

In this question we need to calculate the diagonal of cuboid,
which is =
$$\begin{aligned} \sqrt{l^2+b^2+h^2} \\ = \sqrt{8^2+6^2+2^2} \\ = \sqrt{104} \\ = 2\sqrt{26} \end{aligned}$$

Answer: Option B

Explanation:

Volume is given, we can calculate the radius from it, then by calculating slant height, we can get curved surface area.
$$\begin{aligned} \frac{1}{3}*\pi *r^2*h = 1232 \\ \frac{1}{3}*\frac{22}{7}*r^2*24 = 1232 \\ r^2 = \frac{1232*7*3}{22*24} = 49 \\ r = 7 \\ \text{Now, r = 7cm and h = 24 cm } \\ l = \sqrt{r^2+h^2} \\ = \sqrt{7^2+24^2} = 25cm \\ \text{Curved surface area =}\pi rl\\ = \frac{22}{7}*7*25 = 550 cm^2 \end{aligned}$$

Answer: Option D

Explanation:

To solve this type of question, simply divide the volume of wall with the volume of brick to get the numbers of required bricks
So lets solve this

Number of bricks =
$$\begin{aligned} \frac{\text{Volume of wall}}{\text{Volume of 1 brick}} \\ = \frac{800*600*22.5}{25*11.25*6} \\ = 6400 \end{aligned}$$