- A0
- B−5
- C1
- D
Step-by-Step Solution
Natural numbers start at 1; whole numbers are the naturals together with 0. So 0 is whole but not natural. −5 is an integer (not whole), 1 is natural, and is only rational.
Answer: A) 0
Which number is a whole number but NOT a natural number?
Class 9Number SystemsNumber Systems
Key idea: Number-system hierarchy
Each system contains the previous one:
ℕ ⊂ W ⊂ ℤ ⊂ ℚ ⊂ ℝ
- Natural → add 0 → Whole.
- Whole → add negatives → Integers.
- Integers → allow division (with q ≠ 0) → Rationals.
- Rationals → fill the gaps with irrationals → Reals.
At every step, the new system contains the old, plus more numbers. Real numbers fill the line completely — there are NO gaps in ℝ.
ℕ ⊂ W ⊂ ℤ ⊂ ℚ ⊂ ℝ
- Natural → add 0 → Whole.
- Whole → add negatives → Integers.
- Integers → allow division (with q ≠ 0) → Rationals.
- Rationals → fill the gaps with irrationals → Reals.
At every step, the new system contains the old, plus more numbers. Real numbers fill the line completely — there are NO gaps in ℝ.
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