Hands directly opposite

At what time between 4:00 and 5:00 do a clock's hour and minute hands point in exactly opposite directions (a straight 180180^\circ line)? Give the number of minutes after 4:00, to two decimals.

Show hints (2)+
  1. Write each hand's angle as a function of minutes after 4:00, including the hour hand's 0.50.5^\circ/min drift.
  2. Set (minute - hour) =180= 180^\circ and solve; the hour hand does not stay on the 4.

Answer

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54.55 (± 0.05)

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Asked at: Optiver, IMC

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