See below~
Here, it is given that the radius of a circle is 7 mm and we've to find it's area .
So,
Formula:
[tex] \purple{\boxed{\sf{A = \pi r^2}}} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:[ \pi =\frac{22}{7}][/tex]
Now ,
[tex]\Longrightarrow \sf{A = \pi *r^2}[/tex]
[tex] \: \: \: \: \: \: \: \: \: \: \: \: [/tex]
[tex]\Longrightarrow \sf{A = \frac{22}{7} *7^2}[/tex]
[tex]\: \: \: \: \: \: \: \: \: \: \: \: [/tex]
[tex]\Longrightarrow \sf{A = \frac{22}{7} *49}[/tex]
[tex]\: \: \: \: \: \: \: \: \: \: \: \: [/tex]
[tex]\Longrightarrow \sf{A = \frac{22}{ \cancel7} * \cancel{49}}[/tex]
[tex]\: \: \: \: \: \: \: \: \: \: \: \: [/tex]
[tex]\Longrightarrow \sf{A = 22 * 7}[/tex]
[tex]\: \: \: \: \: \: \: \: \: \: \: \: [/tex]
[tex]\Longrightarrow \sf{A = 154}[/tex]
Therefore , the area of a circle is 154 mm²
