On a given morning the temperature was 81°F. The temperature dropped 9°F and then rose 5°F. How much does the temperature need to rise or fall to return to the initial temperature of 81°F?
1. Rise 4°
2. Rise 9° Rise
3. Fall 4°
4. Fall 5°
To return to the initial temperature of 81°F, the temperature needs to rise by 4°F.
Therefore, the answer is:
1. Rise 4°
To return to the initial temperature of 81°F, we need to calculate the net change in temperature after it dropped 9°F and then rose 5°F.
Net change = Drop + Rise
Net change = -9°F + 5°F
Net change = -4°F
Since the net change is -4°F, the temperature needs to fall 4°F to return to the initial temperature of 81°F. Therefore, the correct option is:
3. Fall 4°
To find out how much the temperature needs to rise or fall to return to the initial temperature of 81°F, we need to reverse the operations that occurred.
First, the temperature dropped 9°F. To reverse this, we need to add 9°F back to the current temperature.
Then, the temperature rose 5°F. Similarly, to reverse this, we need to subtract 5°F from the temperature after the previous step.
Starting with the initial temperature of 81°F:
81°F - 9°F + 5°F = 77°F
So, to return to the initial temperature of 81°F, the temperature needs to rise 4°F. Therefore, the correct answer is:
1. Rise 4°F