Please Help me fix my code

Question

#include<iostream>

using namespace std;

main(){

int number;

cout<<"Please enter the number between 0 to 30: ";

cin>>number;

if(0>=number>=10)

{

cout<<"Blue";

}

else if (11>=number>=20)

{

cout<<"Red";

}

else if (21>=number>=30)

{

cout<<"Green";

}else

cout<<"It is not a correct colour option.";

}

if number is 0 - 10 print blue

if number is 11- 20 print red

if number is 21-30 print green else

it is not a correct colour option

Answer 1

TRY THIS :
#include <iostream>

using namespace std;

int
main ()
{


  int number;

  cout << "Please enter the number between 0 to 30: ";

  cin >> number;

  if (0 <= number && number <= 10)

    {

      cout << "Blue";

    }

  else if (11 <= number && number <= 20)

    {

      cout << "Red";

    }

  else if (21 <= number && number <= 30)

    {

      cout << "Green";

    }
  else
    {
      cout << "It is not a correct colour option.";

    }

  return 0;
}

Answer 2

Problem #1

Your logic is wrong. There aren't any numbers that would be "0>=number>=10" i.e. less or equal to 0 but at the same time greater or equal to 10. The correct logic would be to look for a number that is at least 0 but not larger than 10 (0 <= number <= 10).

The same apply for the rest of the checks.

Problem #2

In many programming languages you cannot exactly use the same expressions as you'd use in mathematics. To tell the C compiler you want to check if a number is at least 0 and is no more than 10 then you have to describe this with two conditions combined together with an and (&&) operator:

0 <= number && number <= 10

Correct Code

#include <iostream>
using namespace std;

main()
{
    int number;
    cout << "Please enter the number between 0 to 30: ";
    cin >> number;
    if (0 <= number && number <= 10)
    {
        cout << "Blue";
    }
    else if (11 <= number && number <= 20)
    {
        cout << "Red";
    }
    else if (21 <= number && number <=30)
    {
        cout << "Green";
    }
    else
    {
        cout << "It is not a correct colour option.";
    }
}