Opposite directions (“pointing towards each other”) in 24 hours — How many times do the hour and minute hands face each other (180° apart) in a day?

Difficulty: Easy

Correct Answer: 22

Explanation:


Introduction / Context:
“Pointing towards each other” is typically interpreted as the hands being in opposite directions, i.e., separated by 180°. Like overlaps, these opposite positions follow a repeating pattern tied to the relative speed of the hands.



Given Data / Assumptions:

  • Relative speed = 5.5° per minute.
  • Opposite positions correspond to an angular difference of 180° (or equivalently −180°).
  • The pattern over any 12-hour span repeats in the next 12 hours.


Concept / Approach:
In 12 hours, opposite positions occur 11 times (analogous to 11 overlaps). Therefore, in 24 hours, the count doubles.



Step-by-Step Solution:
Opposites in 12 hours = 11.Opposites in 24 hours = 2 × 11 = 22.



Verification / Alternative check:
General formula within an hour interval: t (minutes after H:00) satisfies |30H − 5.5t| = 180. Solving across H = 0..10 yields 11 solutions per 12-hour cycle (excluding boundary duplication).



Why Other Options Are Wrong:
24 assumes two per hour, which is incorrect; 20 and 12 undercount the standard result.



Common Pitfalls:
Mixing up counts for right angles (22 per 12 h) with opposites (11 per 12 h).



Final Answer:
22

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