Question

A meteorologist was monitoring the temperature outside in degrees Fahrenheit (∘F)(∘F) and wrote the expression  78+(−6)−578+(−6)−5. Which statement best describes this expression? 

A

The temperature started at  78∘F78^{\circ}\mathrm{F}78∘F and increased by  6∘6^{\circ}6∘ F\mathrm{F}F. Then the temperature decreased by  5∘F5^{\circ}\mathrm{F}5∘F.   

B

The temperature started at  78∘F78^{\circ}\mathrm{F}78∘F and increased by  6∘F6^{\circ}\mathrm{F}6∘F. Then the temperature increased by  5∘F5^{\circ}\mathrm{F}5∘F.  

C

The temperature started ​at  78∘F78^{\circ}\mathrm{F}78∘F and decreased by  6∘F6^{\circ}\mathrm{F}6∘F. Then the temperature decreased by  5∘F5^{\circ}\mathrm{F}5∘F.  ​

D

The temperature started at  78∘F78^{\circ}\mathrm{F}78∘F and decreased by  6∘F6^{\circ}\mathrm{F}6∘F. Then the temperature increased by   5∘F5^{\circ}\mathrm{F}5∘F. 

Answer 1

To analyze the expression \( 78 + (-6) - 5 \):

1. **Starting Temperature**: The temperature begins at \( 78^\circ F \).

2. **First Operation**: The term \( + (-6) \) indicates a decrease of \( 6^\circ F \). So, you subtract \( 6 \) from \( 78 \):
\[
78 - 6 = 72^\circ F
\]

3. **Second Operation**: The term \( -5 \) indicates a further decrease of \( 5^\circ F \). So, you subtract \( 5 \) from \( 72 \):
\[
72 - 5 = 67^\circ F
\]

Putting all of this together:
- The temperature starts at \( 78^\circ F \), decreases by \( 6^\circ F \), and then decreases again by \( 5^\circ F \).

This matches with option **C**: "The temperature started at \( 78^\circ F \) and decreased by \( 6^\circ F \). Then the temperature decreased by \( 5^\circ F \)."

So the correct answer is **C**.