A company decides to drain the water heater to flush out sediments. The water heater has a capacity of 500 gallons. It drains 100 gallons in 20 minutes. After 20 minutes, they open another drain valve and it drains 200 gallons in the next 20 minutes. The drain valves are closed for 10 minutes, while the workers take a break and then the water heater is drained until the water heater is completely empty.

What are the domain and the range of this relation?

The piecewise function represents time in minutes on the x-axis and water in gallons on the y-axis. The function starts from (0, 500), (20, 400), (40, 200), (50, 200), and (70, 0).
x ≥ 0
y ≥ 0
0 ≤ x ≤ 500
0 ≤ x ≤ 70
0 ≤ y ≤ 500
0 ≤ y ≤ 70

1 answer

To analyze the piecewise function you're describing, we need to identify the domain and the range based on the points provided:

  1. Domain: The domain represents the set of possible input values (in this case, time in minutes, denoted as x).

The time values provided are:

  • Start at \( x = 0 \) (initial time)
  • First drain occurs until \( x = 20 \) minutes
  • Second drain valves opened at \( x = 40 \) minutes
  • Break at \( x = 50 \) minutes
  • Finally drained to \( x = 70 \) minutes

Thus, the time spans from 0 minutes to 70 minutes. Therefore, the domain is:

\[ 0 \leq x \leq 70 \]

  1. Range: The range represents the set of possible output values (in this case, water in gallons, denoted as y).

The water values at the key time points are:

  • \( y = 500 \) gallons at \( x = 0 \) minutes,
  • \( y = 400 \) gallons at \( x = 20 \) minutes (after draining 100 gallons),
  • \( y = 200 \) gallons at \( x = 40 \) minutes (after another 200 gallons have been drained),
  • \( y = 200 \) gallons remains at \( x = 50 \) minutes (during break),
  • Finally, \( y = 0 \) gallons at \( x = 70 \) minutes (when the water heater is completely drained).

Thus, the water values span from 0 gallons to 500 gallons. Therefore, the range is:

\[ 0 \leq y \leq 500 \]

In summary, the domain and the range of this relation are:

  • Domain: \( 0 \leq x \leq 70 \)
  • Range: \( 0 \leq y \leq 500 \)