The Challenge
 A properly functioning analog clock shows that it is now 10:10am.
Between now and 9:35am tomorrow morning, how many times will one hand cross over the other hand on this clock?
(No tricks here. The clock will not be tampered with between 10:10am today and 9:35am tomorrow morning. The clock is NOT on board a spacecraft traveling 99.999% of the speed of light, while the observer is on Earth.)
The Correct Answer
Between 10:10am and 9:35am the next day, one hand crosses over the other at these times (approximated to the nearest minute): |
Today
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Tomorrow
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10:55 am
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12:00 am
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12:00 pm
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1:05 am
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1:05 pm
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2:11 am
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2:11 pm
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3:16 am
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3:16 pm
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4:22 am
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4:22 pm
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5:27 am
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5:27 pm
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6:33 am
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6:33 pm
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7:38 am
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7:38 pm
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8:44 am
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8:44 pm
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9:49 pm
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10:55 pm
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The two "gotchas" with this challenge: #1: The hands cross over twenty-two (22) times in a twenty-four (24) hour period, not twenty-four (24) times.
#2: The time elapsed between 10:10am and 9:35am the next morning is twenty-three (23) hours and twenty-five (25) minutes, not twenty-four (24) hours. The 22nd crossover does not occur in this time span.
Click here for an explanation on the internet.
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The Winners
The winners of September's "Mental Gymnastics" challenge are:
- Scott Berndt, Dennis Bahcall Rubber Company. (Kaukauna, WI USA) (first respondent to answer correctly)
- Donald Rossignol, Ohlheiser Corporation (Newington, CT USA) (picked at random from all other correct respondents)
- Joe Peschman, Active Foam Products (Milwaukee, WI USA) (picked at random from all other correct respondents)
- Vicky Bodnar, Fluidtrols Corporation (Westlake, OH USA) (picked at random from all other correct respondents)
- Adam Kline, Eastern Industrial Automation (Newington, NH USA) (picked at random from all other correct respondents)
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