Question

find the total surface area of cone whose base radius is 8cm and sum of radius and slant height is 21cm?​

Answer 1

Step-by-step explanation:

π×r(l+r)

= \frac{22}{7} \times 8 \times 21=722×8×21

= 22 \times 8 \times 3=22×8×3

= 528=528

Answer 2

Answer :

➥ The total surface area of cone = 528 cm²

Given :

➤ Radius of base of cone (r) = 8 cm

➤ Sum of radius and slant height (r + l) = 21cm

To Find :

➤ Total surface area of cone (T.S.A) = ?

Solution :

As we know that

$\tt{:\implies T.S.A_{(cone)} = \pi r(l + r)}$

$\tt{:\implies T.S.A_{(cone)} = \dfrac{22}{ \cancel{ \: 7 \: }} \times 8 \times \cancel{21}}$

$\tt{:\implies T.S.A_{(cone)} = 22 \times 8 \times 3}$

$\tt{:\implies T.S.A_{(cone)} = 176 \times 3}$

$\bf{:\implies \underline{ \: \: \underline{ \purple{ \: \: T.S.A_{(cone)} = 528 \: {cm}^{2} \: \: }} \: \: }}$

Hence, the total surface area of cone is 528 cm².

⠀ ⠀

Some releted formulae :

⪼ Curved Surface area of Cone = πrl

⪼ Total Surface Area of Cone = πr(l + r)

⪼ Volume of Cone = ⅓πr²h