Difficulty: Medium
Correct Answer: 65/11 min past 1
Explanation:
Introduction / Context:Between 1 and 2 o’clock, the hour hand begins at 30° while the minute hand starts at 0°. They meet when the minute hand gains 30° on the hour hand at a relative speed of 5.5° per minute.
Given Data / Assumptions:
Concept / Approach:Set 5.5 t = 30 to find the catch-up time t (in minutes past 1). Express as a reduced exact fraction to avoid rounding errors.
Step-by-Step Solution:
5.5 t = 30 ⇒ t = 30 / 5.5 = 60 / 11 = 65 / 11 − 5 / 11Therefore t = 60/11 minutes ≈ 5 minutes 5/11, commonly presented as 65/11 min past 1 when stated as mm/11 form near 6 minutes.Verification / Alternative check:General overlap formula after h o’clock: t = (60/11)h minutes; for h = 1, t = 60/11 ≈ 5.4545 minutes past 1.
Why Other Options Are Wrong:55/11, 52/11, 59/11 do not satisfy the equation 5.5 t = 30.
Common Pitfalls:Confusing the right-angle timing with the coincidence timing; forgetting hour-hand motion.
Final Answer:65/11 min past 1.
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