Question

2. Find the total surface area of a cone, if its slant height is 21 m and diameter of its base is 24 cm​

Answer 1

Question

Find the total surface area of a cone, if its slant height is 21 m and diameter of its base is 24 cm.

Given

• Slant height of cone 21 m ( changing into cm )
• slant height of cone 21 × 100 = 2100 cm
• Diameter of its base is 24cm
• Radius of cone 24/2 = 12cm

Find

• Total surface Area of cone ?

Formula

Total surface Area of cone πr² + πrl

Solution

$\tt Area_{(Total\:surface\:area\:of\:cone)}= \dfrac{22}{7}× 12^2+\dfrac{22}{7}×12×2100$

$\tt Area_{(Total\:surface\:area\:of\:cone)}= \dfrac{22}{7}×144+22×12×300$

$\tt Area_{(Total\:surface\:area\:of\:cone)}=22×20.571+22×3600$

$\tt Area_{(Total\:surface\:area\:of\:cone)}=452.571+79200$

$\tt Area_{(Total\:surface\:area\:of\:cone)}=1244571 cm^2$

Hence

• Total surface area of cone is 1244571 cm²

Answer 2

Given

Slant height of cone 21 m ( changing into cm )

slant height of cone 21 × 100 = 2100 cm

Diameter of its base is 24cm

Radius of cone 24/2 = 12cm

Find

Total surface Area of cone ?

Formula

Total surface Area of cone πr² + πrl

Solution

\tt Area_{(Total\:surface\:area\:of\:cone)}= \dfrac{22}{7}× 12^2+\dfrac{22}{7}×12×2100Area

(Totalsurfaceareaofcone)

=

7

22

×12

2

+

7

22

×12×2100

\tt Area_{(Total\:surface\:area\:of\:cone)}= \dfrac{22}{7}×144+22×12×300Area

(Totalsurfaceareaofcone)

=

7

22

×144+22×12×300

\tt Area_{(Total\:surface\:area\:of\:cone)}=22×20.571+22×3600Area

(Totalsurfaceareaofcone)

=22×20.571+22×3600

\tt Area_{(Total\:surface\:area\:of\:cone)}=452.571+79200Area

(Totalsurfaceareaofcone)

=452.571+79200

\tt Area_{(Total\:surface\:area\:of\:cone)}=1244571 cm^2Area

(Totalsurfaceareaofcone)

=1244571cm

2

Hence

Total surface area of cone is 1244571 cm²