Find the two-digit number — which statements suffice? I. The difference between the number and its digit-reversed form is 27. II. The difference between the two digits is 3. III. The units digit is less than the tens digit by 3.

Difficulty: Medium

Correct Answer: None of these

Explanation:


Introduction / Context:
We must decide which statements allow us to identify a unique two-digit number. Represent the number as 10a + b with digits a (tens) and b (units).


Given Data / Assumptions:

  • I: |(10a + b) − (10b + a)| = 27 ⇒ 9 * |a − b| = 27 ⇒ |a − b| = 3.
  • II: |a − b| = 3.
  • III: b = a − 3 (units less than tens by 3).


Concept / Approach:
Combine conditions and see if a unique (a, b) pair emerges. With |a − b| = 3 and 1 ≤ a ≤ 9, 0 ≤ b ≤ 9, many numbers satisfy the constraints.


Step-by-Step Solution:

From I: |a − b| = 3.From II: |a − b| = 3 (duplicate of I).From III: b = a − 3, which is one orientation of the absolute difference.Numbers satisfying III include 41, 52, 63, 74, 85, 96 (all valid two-digit numbers).Even with all three, multiple solutions exist; hence no unique number can be determined.


Verification / Alternative check:
Test any candidate from the set; each meets I, II, III and yields the same 27 difference from its reverse. Non-uniqueness persists.


Why Other Options Are Wrong:

  • Only I and II: Merely restate |a − b| = 3 ⇒ many solutions.
  • Only I and III: Still produces a family of solutions with a − b = 3.
  • Only I and either II or III: Same issue; no uniqueness.
  • All I, II and III: Still not unique.


Common Pitfalls:
Assuming the difference with reverse fixes the number; it fixes only the digit gap.


Final Answer:
None of these

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