2. Temperature-conversion program that gives the user the option of converting Fahrenheit to Celsius or Celsius to Fahrenheit. Then carry out the conversion.

Chapter 3: 

Loops and Decisions

Programming Exercise

Problem # 2:

Write a temperature-conversion program that gives the user the option of converting Fahrenheit to Celsius or Celsius to Fahrenheit. Then carry out the conversion. Use floating-point numbers. Interaction with the program might look like this:
Type 1 to convert Fahrenheit to Celsius,
2 to convert Celsius to Fahrenheit: 1
Enter temperature in Fahrenheit: 70
In Celsius that’s 21.111111

Solution:

#include<iostream>
using namespace std;
int main()
{
    int num;
    float cel, faren;
  
    cout<<"Type 1 to convert Fahrenheit to Celsius,"<<endl<<"2 to convert Celsius to Fahrenheit:";
    cin>>num;
  
    if(num==1)
    {
        cout<<"Enter temperature in Fahrenheit: ";
        cin>>faren;
        cel=(faren-32)*5/9;
        cout<<"In Celsius that's "<<cel<<endl;
    }
    else if(num==2)
    {
        cout<<"Enter temperature in Celsius: ";
        cin>>cel;
        faren=(cel*9/5)+32;
        cout<<"In Fahrenheit that's "<<faren<<endl;
    }
    else
    {
        cout<<"Invalid input.";
    }
  
    return 0;
}

Let me know in the comment section if you have any question.

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