In this post, we will learn how to write a simple interest program in Python by taking input from the user and also we will write this program using the function with a detailed explanation and algorithm.

But before we jump into the algorithm or programming part let’s first discuss the formula of simple interest.

## Formula of Simple Interest

**Where, **

- P = principal amount
- R = Rate of interest
- T = Time period

## Algorithm for Simple Interest

- Take input from the user (
,`p`

,`r`

)`t`

- To store the result create a variable called
and do step-3`simple_interest`

`simple_interest = (p * r * t)/100`

- At last print the result (
)`print(simple_interest)`

From the above algorithm, we understood how to write a Python program to calculate simple interest. So now let us do it practically.

Few programming concepts you have to know before writing this program:

### Source Code

```
p = int(input("Enter Principal Amount: "))
r = int(input("Enter Rate of Interest: "))
t = int(input("Enter Time Period: "))
simple_interest = (p*r*t)/100
print(f"Simple Interest is: {simple_interest}")
```

### Output

```
Enter Principal Amount: 50000
Enter Rate of Interest: 10
Enter Time Period: 3
Simple Interest is: 15000.0
```

Now let us modify the above program and write it using the function.

## Simple Interest Program in Python Using Function

Before writing this program Few programming concepts you have to know:

### Source Code

```
def Cal_SI(p,r,t):
return (p*r*t)/100
principal = int(input("Enter Principal Amount: "))
rate = int(input("Enter Rate of Interest: "))
time = int(input("Enter Time Period: "))
print(f"Simple Interest is: {Cal_SI(principal,rate,time)}")
```

### Output

```
Enter Principal Amount: 250000
Enter Rate of Interest: 7
Enter Time Period: 7
Simple Interest is: 122500.0
```