A temple bell rings every 45 minutes at regular intervals. The last bell rang 5 minutes ago, and the next bell is due at 7:45 a.m. At what time did the priest give this information to the devotee?
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A7 : 00 am
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B7 : 05 am
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C7 : 40 am
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D6 : 55 am
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ENone of these
Answer
Correct Answer: 7 : 05 am
Explanation
Introduction / Context:Periodic-event problems hinge on the fixed interval and the relationship between the last occurrence, the next occurrence, and the current time. Here, the bell period is 45 minutes.
Given Data / Assumptions:
- Interval = 45 minutes.
- Last bell = 5 minutes ago from the time of speaking.
- Next bell time = 7:45 a.m.
Concept / Approach:If the next ring is at 7:45 a.m., the previous one must have been at 7:00 a.m. (exactly 45 minutes earlier). Since the last ring was 5 minutes before the speech, the speech was delivered 5 minutes after 7:00 a.m.
Step-by-Step Solution:
Next = 7:45 ⇒ Previous = 7:00Speech time = 7:00 + 5 minutes = 7:05 a.m.Verification / Alternative check:Forward check: after 7:05 a.m., the next ring is indeed at 7:45 a.m. in 40 minutes (because interval is 45; 5 minutes have passed since 7:00).
Why Other Options Are Wrong:7:00 a.m. contradicts “last bell 5 minutes ago”; 7:40 a.m. would place the “last bell” at 6:55 a.m., which is not 45 minutes before 7:40 a.m. relative to the 7:45 schedule.
Common Pitfalls:Adding instead of subtracting with the 45-minute interval, or mixing up which time is “next” vs “previous.”
Final Answer:7 : 05 am.