Problem Solving Work Backward
The test that Keyshawn's class took finished at 10:30 a.m. The first part of the test took 30 minutes. There was a 15 minute break. The second part of the test also took 30 minutes. At what time did the test start?
9:15 am. Answer could vary depending on location of Testing. For example if the class were in an airplane it is possible to start the test in one time zone and finish in another.
To find out what time the test started, we can work backward from the given information.
1. We know that the second part of the test took 30 minutes, and there was a 15-minute break between the two parts. So, the second part of the test and the break combined took 30 + 15 = 45 minutes.
2. We also know that the first part of the test took 30 minutes.
3. Adding the time for both parts of the test, we have a total of 45 + 30 = 75 minutes.
4. Since the test finished at 10:30 a.m., we subtract 75 minutes from 10:30 a.m. to find the starting time.
10:30 a.m. - 75 minutes = 9:55 a.m.
Therefore, the test started at 9:55 a.m.
To find out the start time of the test, we can work backward by subtracting the durations of each part of the test and the break from the finish time.
1. Start with the finish time: 10:30 a.m.
2. Subtract the duration of the second part of the test: 10:30 a.m. - 30 minutes = 10:00 a.m.
3. Subtract the duration of the break: 10:00 a.m. - 15 minutes = 9:45 a.m.
4. Subtract the duration of the first part of the test: 9:45 a.m. - 30 minutes = 9:15 a.m.
Therefore, the test started at 9:15 a.m.