Which sets of numbers are closed under subtraction?

Choose all answers that are correct.

A.
odd natural numbers

B.
rational numbers

C.
{0, 1}

D.
{0, 1, 2}

Question

Which sets of numbers are closed under subtraction?
 
Choose all answers that are correct.
 
 A.
odd natural numbers
 
 B.
rational numbers
 
 C.
{0, 1}
 
 D.
{0, 1, 2}

zepdrix · Answer

Take a sample from each set and see if you're able to leave the set :)

zepdrix · Answer

Odd Naturals:

3 - 5 = -2

Oops, we fell out of the set of Odd Naturals! :O
No closure.
ya?

zepdrix · Answer

C and D are kind of tricky.
If your set contains only 0 and 1,
is there any way you can leave that set by using subtraction?
$\Large\rm 1-0=0$  <-- Hmm this is ok.
$\Large\rm 0-1=-1$ <-- Oops! We left the set {0,1} :O

agl202 · Answer

i think only b is correct because when you subtract two rational numbers, you always get back a rational number.