At what time between 2 and 3 O’clock will the hands of the clock be opposite?

2022

At what time between 2 and 3 O’clock will the hands of the clock be opposite?

  1. A.

    2 hr. 45 min.

  2. B.

    3 O’clock

  3. C.

    2 hr. 43 7/11 min.

  4. D.

    2 hr. 35 min.

Attempted by 72 students.

Show answer & explanation

Correct answer: C

Let the time be 2 : t minutes.

  • Angle of hour hand = 30×2 + 0.5t = 60 + 0.5t degrees.

  • Angle of minute hand = 6t degrees.

For the hands to be opposite, the difference between the angles must be 180°:

  1. |6t − (60 + 0.5t)| = 180

  2. Solve the positive case 6t − 60 − 0.5t = 180 ⇒ 5.5t − 60 = 180 ⇒ 5.5t = 240 ⇒ t = 240/5.5 = 480/11 = 43 7/11 minutes.

  3. The negative case gives a negative t (not in the interval 0–60), so discard it.

Convert the fractional minute to seconds if desired: 7/11 minute = (7/11)×60 = 420/11 = 38 2/11 seconds (≈ 38.18 s).

Final answer: 2 hr 43 7/11 min (approximately 2:43:38.18).

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