Reposted because it was originally posted as a reply to another student's question.
School started at 8:05 a.m. and ended at 2:40 p.m. The work below shows Erica’s calculation of the length of the school day.
Which two errors did Erica make?
1.She subtracted instead of adding the times.
2.She subtracted the end time from the start time.
3.She did not regroup 1 hour for 60 minutes to subtract the minutes.
4.She did not account for a.m. and p.m. in the start and end times.
5.She switched the hours and minutes in both the start and end times.
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posted by efgeyfgeyfegfeygfyegfgeyf
today at 5:46pm
If you copied and pasted Erica's computation, that does not work here and we can not see it.
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posted by Damon
today at 5:50pm
It is lacking the input needed anyway.
dang ma, looks like you can hit it *dabs*
To identify the errors made by Erica, let's analyze her calculation:
Start time: 8:05 a.m.
End time: 2:40 p.m.
Erica's calculation: Subtract the end time from the start time.
2:40 p.m. - 8:05 a.m.
The two errors made by Erica are the following:
1. She subtracted instead of adding the times.
Instead of subtracting the end time from the start time, Erica should have added the times together to calculate the length of the school day.
2. She did not regroup 1 hour for 60 minutes to subtract the minutes.
When subtracting the minutes, Erica did not account for the fact that there are 60 minutes in an hour. Therefore, her calculation of the minutes is incorrect.
To correctly calculate the length of the school day, Erica should have done the following:
1. Convert the time to a 24-hour format for easier calculation (8:05 a.m. becomes 08:05, and 2:40 p.m. becomes 14:40).
2. Calculate the number of hours by subtracting the start time from the end time (14 - 8 = 6 hours).
3. Calculate the number of minutes by subtracting the minutes of the start time from the minutes of the end time (40 - 5 = 35 minutes).
4. If the minutes are negative, borrow 60 minutes from the hours and adjust the number of hours accordingly (35 minutes become -25 minutes and 6 hours become 5 hours).
5. Combine the hours and minutes: 5 hours and 25 minutes.
Therefore, the two errors made by Erica are:
1. She subtracted instead of adding the times.
2. She did not regroup 1 hour for 60 minutes to subtract the minutes.