Question

PLEASE HELP ASAP (MORE THEN ONE ANSWER)

Answer 1

When we say "closed under addition" in the context of rational numbers, we mean to say that when we add up rational numbers then, the sum is also a rational number. 

From the given choices above, the one that should the characteristic of being "closed under addition" is only fourth equation. Both 1/2 and 0.5 are rational numbers. On the other hand, 1 is also a rational number.