### Program 173:Calculate Simple Interest in all Ways

Program 173:             Learn Switch case in detail

```#include<stdio.h>
main()
{
float p,r,t,simpleInterest;
int choice;
printf("Enter\n1 to find out Simple Interest\n2 to find out Principal\n3 to find out rate in % \n4 to find out Time\n");
scanf("%d",&choice);
switch(choice)
{
case 1:
{
printf("Enter Pricipal\n");
scanf("%f",&p);
printf("Enter Rate in percentage \n");
scanf("%f",&r);
printf("Enter Time in years(decimals)\n");
scanf("%f",&t);

simpleInterest=(float)(p*r*t)/100.0;
printf("Simple Interest is %f\n",simpleInterest);
break;
}
case 2:
{
printf("Enter Simple Interest\n");
scanf("%f",&simpleInterest);
printf("Enter Rate in percentage\n");
scanf("%f",&r);
printf("Enter Time in years(decimals)\n");
scanf("%f",&t);
p=(float)(100.0*simpleInterest)/(r*t);
printf("Principal is %f\n",p);
break;

}
case 3:
{
printf("Enter Simple Interest\n");
scanf("%f",&simpleInterest);
printf("Enter Principal\n");
scanf("%f",&p);
printf("Enter Time in years(decimals)\n");
scanf("%f",&t);
r=(float)(100.0*simpleInterest)/(p*t);
printf("Rate is %f%\n",r);
break;
}
case 4:
{
printf("Enter Simple Interest\n");
scanf("%f",&simpleInterest);
printf("Enter Principal\n");
scanf("%f",&p);
printf("Enter Rate in percentage\n");
scanf("%f",&r);
t=(float)((100.0*simpleInterest)/(p*r));
printf("Time is %f years\n",t);
break;
}
}
}

```
Explanation:
Formulae used in Program:
```1.Simple Interest=(Principal*Rate in %* Time in Years)/100

2.Principal=(100*Simple Interest)/(Rate in %* Time in Years)

3.Rate(%)=(100*Simple Interest)/(Principal* Time in Years)

4.Time(Yrs)=(100*Simple Interest)/(Principal* Rate(%)) ```

1. This program starts with initializing :
• p → To store principal in Rupees
• r → To store rate in %
• t → To store time in years
• simpleInterest → To store output
2. ```printf("Enter\n1 to find out Simple Interest\n2 to find out Principal\n
3 to find out rate in % \n4 to find out Time\n");
scanf("%d",&choice);```
To prompt user to choose one of the following as shown in the output.
3. Lets run by giving choice as 2 which is to find out Principal.
4. As the choice is 2. Case 2: will be executed. Learn Switch case in detail
• As per case formula 2 is used for execution
• ``` printf("Enter Simple Interest\n");
scanf("%f",&simpleInterest);```
Taking Simple Interest from user
```    printf("Enter Rate in percentage\n");
scanf("%f",&r);```
Taking Rate from user
```    printf("Enter Time in years(decimals)\n");
scanf("%f",&t);```
Taking Time from user
```    p=(float)(100.0*simpleInterest)/(r*t);
printf("Principal is %f\n",p);
break;```
From formula 2 the above will calculate and stores result in p which is then printed.

Output: