Question

Titus works at a hotel. Part of his job is to keep the complimentary pitcher of water at least half full and always with ice. When he starts his shift, the water level shows 4 gallons, or 128 cups of water. As the shift progresses, he records the level of the water every 10 minutes. After 2 hours, he uses a regression calculator to compute an equation for the decrease in water. His equation is W –0.414t + 129.549, where t is the number of minutes and W is the level of water. According to the equation, after about how many minutes would the water level be less than or equal to 64 cups

Answer 1

Let W= -0.414t + 129.549 be the given equation. For finding the value of t, we have to solve inequation and search for the unknown t value. That is as follow: -0.414t + 129.549

Answer 2

The correct answer is:

t ≥ 158.33, or rounded, t ≥ 160.

Explanation:

The equation we're given is 
W = -0.414t + 129.549, which an be written as
-0.414t + 129.549 = W.

We are asked to find the amount of time it would take for the water level to be less than or equal to 64 cups.  Plugging this information in, we have:

-0.414t + 129.549 ≤ 64

To solve this, we first cancel 129.549 by subtracting from both sides:
-0.414t + 129.549 - 129.549 ≤ 64 - 129.549
-0.414t ≤ -65.549

Now divide both sides by -0.414:
-0.414t/-0.414 ≤ -65.549/-0.414
t ≥ 158.33

(When we multiply or divide both sides of an inequality by a negative number, we must flip the inequality symbol.)