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.

7hr 65
8 hr 5 min -
2hr 40 min
---------------
5hr 25 minutes

Which two errors did Erica make?

Also if you are trying to find the answers to choose it's

A. She subtracted instead of adding the times.
B. She subtracted the end time from the start time.
C. She did not regroup 1 hour for 60 minutes to subtract the minutes.
D. She did not account for a.m. and p.m. in the start and end times.
E. She switched the hours and minutes in both the start and end times.

Choose two.

Who knows how she got that

Maybe that cumbersome method of pm and am got in the way.
2:40 pm -----> 14:40
8:05 am -----> 8:05

14:40 - 8:05 = 6:35

On you calculator, look for a key similar to D°M'S
This will allow you to do addition and subtraction
of units of time, D would be hours, M is minutes and S is seconds
The original intent was to do operations of units and angles, but
since units of time of hours, minutes, seconds are structured in the
same way as angles in degrees, minutes and seconds, it serves
well for both units.

1.b, d

To identify the errors Erica made, let's analyze her calculation step by step:

1. Erica correctly subtracted the time school started from the time it ended: 2 hours and 40 minutes.
2. However, she made two errors in converting the time to hours and minutes:

Error 1: Erica added the hours and minutes incorrectly. Instead of adding the hours and minutes separately, she incorrectly added them together as 8 hours and 5 minutes.

Error 2: Erica subtracted the wrong value for the starting time. She subtracted 7 hours and 65 minutes, which is incorrect.

Correct calculation:

To find the length of the school day, we need to subtract the starting time from the ending time.

Step 1: Convert the starting time to minutes: 8 hours and 5 minutes can be expressed as 8 * 60 + 5 = 485 minutes.

Step 2: Subtract the starting time (485 minutes) from the ending time (2 hours and 40 minutes).
2 hours and 40 minutes can be expressed as 2 * 60 + 40 = 160 minutes.

Step 3: Subtract the starting time (485 minutes) from the ending time (160 minutes) to find the duration of the school day.
485 minutes - 160 minutes = 325 minutes.

Step 4: Convert the duration from minutes to hours and minutes.
325 minutes can be expressed as 5 hours and 25 minutes.

So, Erica made two errors in her calculation:
1. Erica incorrectly added the hours and minutes together instead of adding them separately.
2. Erica subtracted the wrong value for the starting time.