Interior points subsets of R

Find the set of interior points for each of these subsets of R (real #s).
(a) (-1, 1)
(b) (-1, 1]
(c) Q (rational #s)
(d) R - Q (irrational #s)

attempted answers:
(a) (-1, 1)
(b) (-1, 1)
(c) R - Q
(d) R - Q

I was just wondering whether or not these answers where correct or not.
Thanks

Quote:

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Originally Posted by tbyou87

Find the set of interior points for each of these subsets of R (real #s).
(a) (-1, 1)
(b) (-1, 1]
(c) Q (rational #s)
(d) R - Q (irrational #s)

attempted answers:
(a) (-1, 1)
(b) (-1, 1)
(c) R - Q
(d) R - Q

I was just wondering whether or not these answers where correct or not.
Thanks

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(a) and (b) are OK.

(c) is the empty set (there are no interior points of Q, as every open interval
containing a rational also contains an irrational)

(d) same as (c) (there are no interior points of R-Q, as every open interval
containing an irrational also contains an rational)

RonL