Question

From a solid right circular cylinder of height 2.4 cm

Answer 1

in this question not decide

Answer 2

Appropriate Question:

From a solid cylinder whose height is 2.4 cm and diameter 1.4 cm , a conical cavity of the same height and same diameter is hollowed out .Find the total surface area of remaining solid.

Solution :

It is given that ,

Diameter of the cylinder = 1.4 cm

Radius of cylinder = 1.4 / 2 = 0.7 cm

Height of the cylinder = 2.4 cm

Firstly , we wI'll find the slant height of cone , Therefore;

$\sf{}l = \sqrt{ {r}^{2} + {h}^{2} } \\ \\ \sf{}l = \sqrt{(0.7) ^{2} + { {(2.4)}^{2} } } \\ \\ \sf{}l = \sqrt{0.49 + 5.75} \\ \\ \sf{}l = \sqrt{6.25} \\ \\ \boxed{ \sf{}l = 2.5 \: cm}$

Therefore, Slant height of the cone is equals to 2.5 cm .

Now , Total surface area of remaining solid = curved surface area of the cylinder+ area of the base of the cylinder + curved surface area of the cone .

$\sf{} = 2\pi \: rh + \pi {r}^{2} + \pi \: rl \\ \\ \sf{} = (2 \times \frac{22}{7} \times 0.7 \times 2.4 + \frac{22}{7} \times ( {07)}^{2} + \frac{22}{7} \times 0.7 \times 2.5) {cm}^{2} \\ \\ \sf{} = 44 \times 0.1 \times 2.4 \times 22 \times 0.1 \times 0.7 + 22 \times 0.1 \times 2.5 \\ \\ \sf{} = 10.56 + 1.54 + 5.5 \: {cm}^{2} \\ \\ \sf{} = 17.6 {cm}^{2}$

Therefore , total surface area is equals to 18 cm².

$\underline{ \underline{ \sf{ \red{ \bold{ More \: Formulas}}}}} \\ \\ \: \sf{}voume \: of \: cube \: = {a}^{3} \\ \\ \sf{}volume \: of \: cylinder = \pi {r}^{2} h \\ \\ \sf{}volume \: of \: cone = \frac{1}{3} \pi \: {r}^{2} h \\ \\ \sf{}volume \: of \: sphere \: = \frac{4}{3} \pi \: {r}^{3} \\ \\ \sf{} volume \: of \: hemisphere = \frac{2}{3} \pi {r}^{3}$