The base radius of a cone is 21 cm and the height is 28cm, then, whic…

The correct answer is Option (3) → (C), (D) and (A) only

Given:

• Radius $r = 21$ cm
• Height $h = 28$ cm

Slant height

$l = \sqrt{r^2 + h^2} = \sqrt{21^2 + 28^2} = \sqrt{441 + 784} = \sqrt{1225} = 35 \text{ cm}$

(A) is correct
(B) is incorrect

Volume of the cone

$V = \frac{1}{3}\pi r^2 h = \frac{1}{3}\pi (21)^2(28)$

$= \frac{1}{3}\pi (441)(28) = 4116\pi$

Using $\pi = \frac{22}{7}$​:

$V = 4116 \times \frac{22}{7} = 12936 \text{ cm}^3$

(C) is correct

Curved Surface Area (CSA)

$\text{CSA} = \pi r\, l = \pi \times 21 \times 35$

$= 735\pi = 735 \times \frac{22}{7} = 2310 \text{ cm}^2$

(D) is correct

Correct statements: (A), (C), and (D)