The teacher told the students, “The school bell is rung at regular intervals…
2021
The teacher told the students, “The school bell is rung at regular intervals of 45 minutes. The last bell was rung five minutes ago. The next bell is due to be rung at 7.45 am.” At what time did the teacher give this information to the students?
Answer: A. 7.05 am — ConceptA fixed interval means that consecutive bell times differ by exactly the same duration. To locate a time within such an interval, first move backward…
- A.
7.05 am
- B.
7.40 am
- C.
7.00 am
- D.
6.55 am
Attempted by 4 students.
Show answer & explanation
Correct answer: A
Concept
A fixed interval means that consecutive bell times differ by exactly the same duration.
To locate a time within such an interval, first move backward from a known future bell to the preceding bell, then add the stated elapsed time.
Application
The next bell is due at 7.45 am, and consecutive bells are 45 minutes apart.
Previous bell time = 7.45 am − 45 minutes = 7.00 am.
The teacher spoke five minutes after that bell: 7.00 am + 5 minutes = 7.05 am.
Cross-check
Five minutes before 7.05 am is 7.00 am; adding the 45-minute interval gives 7.45 am, which matches the stated next bell.
Therefore, the teacher gave the information at 7.05 am.