Sebastian was in a hotel lobby and took the elevator up 7 floors to his room. Then he took the elevator down 9 floors to the parking garage. He described his movement with the expression below.

Question

9+(−7)



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(1 point)
Responses

Sebastian should have started at zero before adding –7.
Sebastian should have started at zero before adding –7.

Sebastian should have switched the two addends and written −7+9
.
Sebastian should have switched the two addends and written negative 7 plus 9.

Sebastian should have used –9 and 7.
Sebastian should have used –9 and 7.

Sebastian should have used 0 and –9.

Answer 1

To represent Sebastian's movement correctly, starting from his original position is important. He goes up 7 floors and then down 9 floors. Since he starts at an initial level (which we can consider as 0), the movements can be expressed as:

1. Moving up 7 floors: +7
2. Moving down 9 floors: -9

So, the appropriate expression to represent his total movement would be:

\(0 + 7 - 9\)

However, if we look at how he described his movement with \(9 + (-7)\), it seems to imply that he starts at 9 (as if he was at the 9th floor before going down). He should be starting from 0, not 9.

Thus, the most accurate response would be:

Sebastian should have started at zero before adding -7.