C++ program to convert speed from miles/h to km/h using class

Learn, how can we convert speed from miles/h to km/h using the class and object approach?
Submitted by Shubh Pachori, on September 04, 2022

Problem statement

Given speed in miles/h, convert it into km/h using class and object approach in C++.

Example:

```Input:
Enter Speed in miles/h :123.1

Output:
Speed in km/h : 198.11
```

C++ code to convert speed from miles/h to km/h using the class and object approach

```#include <iostream>
using namespace std;

// create a class
class Speed {
// private data member
private:
float miles_per_h;

// public member functions
public:
// getSpeed() function to insert
// speed in miles/h
void getSpeed() {
cout << "Enter Speed in miles/h : ";
cin >> miles_per_h;
}

// changeSpeed() function to convert speed
// from miles/h to km/h
double changeSpeed() {
// initializing float type variable to
// store speed in km/h
float km_per_h;

// converting the speed
km_per_h = (miles_per_h / 0.6213712);

// returning the speed
return km_per_h;
}
};

int main() {
// create object
Speed S;

// float type variable to
// store converted speed
float speed;

// calling getSpeed() function to
// insert speed
S.getSpeed();

// calling changeSpeed() function
// to convert speed
speed = S.changeSpeed();

cout << "Speed in km/h : " << speed;

return 0;
}
```

Output

```Enter Speed in miles/h : 222.231
Speed in km/h : 357.646
```

Explanation

In the above code, we have created a class Speed, one float type data member miles_per_h to store the speed in miles/h, and public member functions getSpeed() and changeSpeed() to store speed in miles/h and to convert it to km/h.

In the main() function, we are creating an object S of class Speed, reading the inputted speed by the user using getSpeed() function, and finally calling the changeSpeed() member function to convert it to km/h. The changeSpeed() function contains the logic to convert the speed from miles/h to km/h and printing the result.