A Simple program to convert the temperature from Celsius to Fahrenheit to Kelvin in C

#include<stdio.h>
int main()
{
    printf("Enter the 1 for Celsius to fahrenheit \n 2 for Fahrenheit to Celsius \n and 3 for Kelvin to Celsius\n");
    int opt=0;
    scanf("%d",&opt);
    switch(opt){
    case 1:float tem;
    printf("Enter temperature in Celsius\n");
    scanf("%f",&tem);
    float a1=(tem*9/5)+32;
    printf("Temp=%f\n",a1);
    break;

    case 2:float temp1;
    printf("Enter temperature in Fahrenheit\n");
    scanf("%f",&temp1);
    float a2=(temp1-32)*9/5;
    printf("Temp=%f\n",a2);
    break;

    case 3:float temp2;
    printf("Enter temperature in Kelvin\n");
    scanf("%f",&temp2);
    float a3=temp2-273.15;
    printf("Temp%f\n",a3);
    break;

    default:
    printf("Wrong entry");
    break;
    }
    return 0;
}

To convert Fahrenheit to Celsius we use the formula (32°F − 32) × 5/9 = 0°C.

And To convert from Celsius to Fahrenheit we use the formula (0°C × 9/5) + 32 = 32°F.

And Kelvin to Celsius we use K-273.15.

Thanks ...