Maria created a graph of [tex]\( B(t) \)[/tex], the temperature over time. For the interval between [tex]\( t=3 \)[/tex] and [tex]\( t=7 \)[/tex], the average rate of change in her graph of [tex]\( B(t) \)[/tex] is 8. Which statement must be true?

A. The temperature was 8 degrees higher when [tex]\( t=7 \)[/tex] than when [tex]\( t=3 \)[/tex].
B. The temperature was 8 times higher when [tex]\( t=7 \)[/tex] than when [tex]\( t=3 \)[/tex].
C. The temperature was 32 degrees higher when [tex]\( t=7 \)[/tex] than when [tex]\( t=3 \)[/tex].
D. The temperature was 2 degrees higher when [tex]\( t=7 \)[/tex] than when [tex]\( t=3 \)[/tex].



Answer :

To analyze the given problem and understand which statement must be true, let's break it down step by step.

We're given:
1. The average rate of change in the graph [tex]\( B(t) \)[/tex] over the interval from [tex]\( t = 3 \)[/tex] to [tex]\( t = 7 \)[/tex] is 8. This means the rate at which the temperature changes is 8 degrees per unit time (here, per unit of [tex]\( t \)[/tex]).

The average rate of change formula can be expressed as:
[tex]\[ \text{Rate of change} = \frac{\Delta B}{\Delta t} \][/tex]
Where:
- [tex]\( \Delta B \)[/tex] is the change in temperature,
- [tex]\( \Delta t \)[/tex] is the change in time.

Here, [tex]\( \Delta t \)[/tex] is [tex]\( t_{\text{end}} - t_{\text{start}} \)[/tex]. Given:
[tex]\[ t_{\text{start}} = 3 \quad \text{and} \quad t_{\text{end}} = 7 \][/tex]
So,
[tex]\[ \Delta t = 7 - 3 = 4 \][/tex]

Given the rate of change is 8, we can write the equation:
[tex]\[ 8 = \frac{\Delta B}{4} \][/tex]

To find [tex]\( \Delta B \)[/tex], we rearrange the formula:
[tex]\[ \Delta B = 8 \times 4 = 32 \][/tex]

So, the change in temperature ([tex]\( \Delta B \)[/tex]) over the interval from [tex]\( t = 3 \)[/tex] to [tex]\( t = 7 \)[/tex] is 32 degrees.

This leads us to conclude that the temperature was 32 degrees higher when [tex]\( t = 7 \)[/tex] than when [tex]\( t = 3 \)[/tex].

Therefore, the correct statement must be:
- The temperature was 32 degrees higher when [tex]\( t = 7 \)[/tex] than when [tex]\( t = 3 \)[/tex].