# Calculate area of a circle in C

###### scanf() - Question 13

In this question, we will see how to input the radius of a circle in C programming using the scanf() function and find its area. To know more about scanf() function click on the scanf() function lesson.

**Q13)** Write a program in C to input the radius of a circle and find its area. Area of a circle is πr^{2}. Where r is the radius and the value of π (pie) is 22/7 or 3.142

Formula: area = 3.142 * r * r

#### Program

```
#include <stdio.h>
#include <conio.h>
int main()
{
float r,a;
printf("Enter radius of a circle ");
scanf("%f",&r);
a=3.142*r*r;
printf("Area=%.2f",a);
return 0;
}
```

#### Output

Enter radius of a circle 5 Area=78.55