### Video Transcript

One of addition’s properties is
that the sum of a number and its opposite is always equal to zero. Which of the following situations
does NOT demonstrate this property of addition? Is it A) the school’s football team
lost 10 yards on their first down and lost 10 yards on the second down? Is it B) the school’s football team
lost five yards on their first down and gained five yards on the second down? Is it C) on a Sunday, the
temperature was negative two degrees Fahrenheit outside and two degrees Fahrenheit
inside? D) A ball was kicked 10 metres
upward in the air, and then it fell down 10 metres. Or (E) a bucket descended 100
metres down a well, and then it was lifted 100 metres up the well.

In order to answer this question,
we need to decide which of the five situations does not demonstrate the
property. We are looking for a situation
where the sum is not equal to zero.

In situation, E the bucket
initially descends 100 metres down the well. This is equal to negative 100. It was then lifted 100 metres up
the well. This would be equal to positive
100. The sum of negative 100 and
positive 100 is zero. Therefore, this is not the correct
answer.

In situation D, the ball was kicked
10 metres upward in the air. This would be equal to positive
10. The ball then fell down 10
metres. This would be equal to negative
10. Once again, the sum of these is
equal to zero. Positive 10 plus negative 10 equals
zero. Situation D is not the correct
answer.

In situation C, the temperature
outside was negative two. The temperature inside was two
degrees Fahrenheit, or positive two. Once again, the sum of these two
values is equal to zero, as it is the number two and its opposite. We are now left with two possible
correct answers, option B and option A.

In option B, the school’s football
team lost five yards on their first down. This is equal to negative five. The team gained five yards on the
second down. This is equal to positive five. The sum of negative five and
positive five is zero. Therefore, we can also rule out
option B.

In option A, the football team lost
10 yards on their first down. This is equal to negative 10. They also lost 10 yards on the
their second down, which is also equal to negative 10. Negative 10 plus negative 10 is
equal to negative 20. As this can also be written as
negative 10 minus 10. As this answer is not equal to
zero, situation A is the correct answer.

The situation that does not
demonstrate the property of addition whereby the sum of a number and its opposite is
always equal to zero is situation A. The school’s football team lost 10
yards on their first down and lost 10 yards on the second down.