In this shot, we will learn how to use the `ratio_multiply()` function.

The **`ratio_multiply()` function** is available in the `<ratio>` header file in C++ and is used to multiply two ratios.
 
#     
## What is a ratio?
A **ratio** is a representation of a fraction in which the numerator and denominator are differentiated by the colon (:) symbol. The numerator and denominator can be of `float` data type.

Let’s understand with the help of an example. 
* Suppose that the first ratio is 10 : 3 and the second ratio is 5 : 2.
* The result of the `ratio_multiply()` function for these two ratios is 25 : 3.

* The ratios 10 : 3 and 5 : 2 can be represented as $\frac{10}{3}$ and $\frac{5}{2}$​ in fractional form, respectively.

* The multiplication = $\frac{10}{3}$ * $\frac{5}{2}$ = $\frac{50}{6}$ = $\frac{25}{3}$ 

## Parameters
The `ratio_multiply()` method takes the following parameters:
* `Ratio1`: A `ratio` object for multiplication.
* `Ratio2`: Another `ratio` object to perform the multiplication with the first `ratio` object.

## Return value
`ratio_multiply()` returns the result of multiplication in the simplest form.
The function returns two constants:
* `num`: The simplified numerator of the ratio after the multiplication of the two ratios.
* `den`: The simplified denominator of the ratio after the multiplication of the two ratios.

## Code
Let’s have a look at the code.


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

int main()
{ 
  typedef ratio<10, 3> ratio1;
  typedef ratio<5, 2> ratio2;

  typedef ratio_multiply< ratio1, ratio2 > sum;
    
  cout << "The ratio after multiplication is : ";
  cout << sum::num << "/" << sum::den;
  
  return 0;
}


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## Explanation

* In lines 1 and 2, we import the required header files.
* In line 5, we make a `main()` function.
* In lines 7 and 8, we declare two ratios.

* In line 10, we use the `ratio_multiply()` function to perform the multiplication between the two declared ratios.
* In line 12, we display a message regarding the result.
* In line 13, we display the numerator and denominator by accessing them through the multiplication variable, and display the result.


In this way, we can use the `ratio_multiply()` function to multiply two ratios and get the multiplication in the simplest form.


How to use the ratio_multiply() function in C++

Use `<ratio>`’s ratio_multiply() in C++ to multiply two ratios and get a simplified result.