Question

the curved surface area of a cone whose diameter is 7 cm and height is 4 cm
answer it it's urgent plz​

Answer 1

$\huge \rm {Answer:-}$

__________________________________

$\sf \red {Given:-}$

★Diameter of the cone(d) =7cm

$\colon \to \tt {Diameter=2 \times Radius}$

$\colon \to \tt{7=2 \times Radius}$

$\colon \to \tt { Radius=\frac{7}{2}}$

★ Height of the cone (h)=4 cm

__________________________________

$\sf \blue {To\: Find:-}$

★The curved surface area of a cone=?

__________________________________

$\sf \pink {We\: know,}$

★ Curved surface area of a cone =πrl

★where ,

★l is the slant height.

★so,to find the Curved surface area of a cone slant height (l) is to be calculated.

__________________________________

$\sf \purple {Formula,}$

$\colon \to \tt {l^{2}=r^{2}+h^{2}}$

$\colon \to \tt {l^{2}=(\frac{7}{2})^{2}+(4)^{2}}$

$\colon \to \tt{l^{2}=\frac{7}{2}\times\frac{7}{2}\times4\times4}$

$\colon \to \tt{l^{2}=\frac{49}{4}\times16}$

$\colon \to \tt{l^{2}=\frac{49}{\cancel{4}}\times{\cancel{16}}^{4}}$

$\colon \to \tt{l^{2}=49\times4}$

$\colon \to \tt{l^{2}=196}$

$\colon \to \tt{l=\sqrt196}$

$\colon \implies \tt \green {\fbox{l=14}}$

__________________________________

★Now , supplanting the values in the formula πrl

$\colon \to \tt{\frac{22}{7}\times{\frac{7}{2}}\times 14}$

$\colon \to \tt {\frac{22}{\cancel7}\times{\frac{\cancel7}{\cancel2}}\times {\cancel{14}}^7}$

$\colon \to \tt {22\times7}$

$\colon \implies \tt \green {\fbox{154}}$

__________________________________

$\sf \orange {Hence,}$

★The curved surface area of a cone is ${154cm^{2}}$