High School

A meteorologist predicts the daily high and low temperatures as [tex]91^{\circ} F[/tex] and [tex]69^{\circ} F[/tex]. If [tex]t[/tex] represents the temperature, then this situation can be described with the inequality [tex]69 \leq t \leq 91[/tex]. Which of the following absolute value inequalities is an equivalent way of expressing this?

F. [tex]69 \leq |t| \leq 91[/tex]
G. [tex]|t-80| \leq 11[/tex]
H. [tex]|t-69| \leq 91[/tex]
J. [tex]|t-11| \leq 80[/tex]

Answer :

To solve the problem of finding an equivalent absolute value inequality for the situation [tex]\(69 \leq t \leq 91\)[/tex], let's follow these steps:

1. Identify the Midpoint:
- The midpoint of the given temperature range can be found by averaging the high and low temperatures.
- Calculating the midpoint: [tex]\( \frac{69 + 91}{2} = \frac{160}{2} = 80 \)[/tex].

2. Determine the Range:
- The range is the distance from the midpoint to either the high or low temperature.
- The distance from 80 to 91 (or from 80 to 69) is [tex]\(91 - 80 = 11\)[/tex] (or [tex]\(80 - 69 = 11\)[/tex]).

3. Formulate the Absolute Value Inequality:
- An absolute value inequality representing the interval [tex]\(69 \leq t \leq 91\)[/tex] can be expressed as [tex]\( |t - 80| \leq 11 \)[/tex].
- This is because the absolute value inequality [tex]\( |t - 80| \)[/tex] represents all values [tex]\( t \)[/tex] that are within 11 units of 80, thus capturing the original range from 69 to 91.

Now let's review the provided options:

- F. [tex]\(69 \leq |t| \leq 91\)[/tex]: This combines the temperatures into an incorrect form and is not equivalent to the interval [tex]\(69 \leq t \leq 91\)[/tex].
- G. [tex]\( |t-80| \leq 11 \)[/tex]: This correctly captures our calculated absolute value inequality.
- H. [tex]\( |t-69| \leq 91 \)[/tex]: This does not accurately describe the interval [tex]\(69 \leq t \leq 91\)[/tex].
- J. [tex]\( |t-11| \leq 80 \)[/tex]: This also does not correctly represent the interval [tex]\(69 \leq t \leq 91\)[/tex].

Therefore, the correct answer is:
G. [tex]\( |t-80| \leq 11 \)[/tex].