Quite simply, they are closed under addition. No "when".
Natural (ℕ), integer (ℤ), rational (ℚ), real (ℝ) and complex (ℂ) numbers are all closed under addition.
No. A number cannot be closed under addition: only a set can be closed. The set of rational numbers is closed under addition.
Rational numbers are closed under addition, subtraction, multiplication. They are not closed under division, since you can't divide by zero. However, rational numbers excluding the zero are closed under division.
Yes.
Yes.
Natural (ℕ), integer (ℤ), rational (ℚ), real (ℝ) and complex (ℂ) numbers are all closed under addition.
The set of even numbers is closed under addition, the set of odd numbers is not.
No.
The numbers are not closed under addition because whole numbers, even integers, and natural numbers are closed.
No. A number cannot be closed under addition: only a set can be closed. The set of rational numbers is closed under addition.
Yes. The set of real numbers is closed under addition, subtraction, multiplication. The set of real numbers without zero is closed under division.
yes because real numbers are any number ever made and they can be closed under addition
The complex numbers are a field.
Rational numbers are closed under addition, subtraction, multiplication. They are not closed under division, since you can't divide by zero. However, rational numbers excluding the zero are closed under division.
Sets of numbers that are closed under addition include the integers, rational numbers, real numbers, and complex numbers. This means that when you add any two numbers from these sets, the result will also belong to the same set. For example, adding two integers will always result in another integer. This property is fundamental in mathematics and is essential for performing operations without leaving the set.
Addition.
Yes.