Elapsed Time — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
School starts at 8:30 AM and ends at 3:15 PM, so the school day is 5 hours and 45 minutes long.
Corrected: School starts at 8:30 AM and ends at 3:15 PM, so the school day is 6 hours and 45 minutes long.
From 8:30 AM to 3:30 PM is 7 hours; subtract 15 minutes to land at 3:15 PM, giving 6 hours 45 minutes.
2. Fix the sentence:
Lunch begins at 11:45 AM and ends at 12:25 PM, a duration of 50 minutes.
Corrected: Lunch begins at 11:45 AM and ends at 12:25 PM, a duration of 40 minutes.
11:45 AM to 12:00 PM is 15 minutes, plus 25 more minutes equals 40 minutes total.
3. Fix the sentence:
Recess runs from 10:10 AM to 10:35 AM, so its schedule shows a duration of 35 minutes.
Corrected: Recess runs from 10:10 AM to 10:35 AM, so its schedule shows a duration of 25 minutes.
Both times are within the 10 AM hour, so 35 minus 10 equals 25 minutes.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A Grade 4 art class begins at 1:20 PM and ends at 2:05 PM. The duration is 45 minutes.
1:20 PM to 2:00 PM is 40 minutes, and 2:00 to 2:05 is 5 more, totaling 45 minutes.
2. The Grade 4 morning bell rings at 7:55 AM and homeroom ends at 8:40 AM. The duration is 45 minutes.
7:55 to 8:00 is 5 minutes, plus 40 more minutes to 8:40, equals 45 minutes.
3. A Grade 4 reading block starts at 9:15 AM and ends at 10:00 AM. Its duration is 45 minutes.
From 9:15 AM up to 10:00 AM is exactly 45 minutes.
4. The Grade 4 school day schedule shows arrival at 8:30 AM and dismissal at 3:15 PM, a duration of 6 hours and 45 minutes.
8:30 AM to 2:30 PM equals 6 hours, and 2:30 PM to 3:15 PM is another 45 minutes.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. A Grade 4 student's schedule shows math from 9:00 AM to 9:50 AM and science from 10:00 AM to 10:45 AM. What is the total class duration?
Sample answer: Math lasts 50 minutes and science lasts 45 minutes, so the total duration is 95 minutes, or 1 hour and 35 minutes.
50 minutes plus 45 minutes equals 95 minutes, which converts to 1 hour 35 minutes.
2. A Grade 4 after-school program runs from 3:30 PM to 5:15 PM. What is its duration?
Sample answer: From 3:30 PM to 5:00 PM is 1 hour 30 minutes, plus 15 more minutes equals 1 hour and 45 minutes.
3:30 PM to 5:30 PM would be 2 hours; subtract 15 minutes to reach 5:15 PM, giving 1 hour 45 minutes.