No.
Yes.
yes
Yes
Yes, it is closed. This means that if you multiply two even number, you again get a number within the set of even numbers.
Yes.natural numbers are closed under multiplication.It means when the operation is done with natural numbers in multiplication the sum of two numbers is always the natural number.
Is { 0, 20 } closed under multiplication
No.
No.
No.
No.
Yes they are closed under multiplication, addition, and subtraction.
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!
Yes.
Yes.