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This clock was set right at the time shown and gains 15 seconds every hour. After how many days will it next show the correct time again?

Competition practiceClocks
  • A240 days
  • B10 days
  • C60 days
  • D120 days

Step-by-Step Solution

A 12-hour dial shows the correct time again once it has gained 12 h = 720 min. It gains 15 s × 24 = 6 min a day, so 720 ÷ 6 = 120 days. (240 days waits for a full 24 h gain; 10 days is when it is 1 hour ahead.)
Answer: D) 120 days

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