For a science fair project, Felicia measured the height of a candle as it burned. The table shows the linear relationship between the height of the candle and the number of minutes it burned for.

Candle
Time (minutes) Height
(mm)
1 8,000
2 6,000
3 4,000
4 2,000
5 0

Which function can be used to find y, the height of the candle after it has burned for x minutes?
Responses
A y = 2,000x + 10,000y = 2,000 x + 10,000
B y = 10,000x + 2,000y = 10,000 x + 2,000
C y = -10,000x + 12,000y = -10,000 x + 12,000
D y = -2,000x + 10,000

1 answer

To find the correct linear function that models the height of the candle (y) based on the number of minutes it has burned (x), we can analyze the data provided:

From the data:

  • When x = 1, y = 8,000
  • When x = 2, y = 6,000
  • When x = 3, y = 4,000
  • When x = 4, y = 2,000
  • When x = 5, y = 0

From the observations, we can determine that the height decreases by 2,000 mm for each additional minute burned. The slope of the function (the rate of change) is -2,000 mm per minute.

Next, we need to find the y-intercept. When the candle has burned for 0 minutes (x = 0), its height starts at 10,000 mm. Thus, when x = 0, y = 10,000.

Now we can write the linear equation in the form y = mx + b, where m is the slope and b is the y-intercept:

  • Slope (m) = -2,000
  • y-intercept (b) = 10,000

Thus, the function is: \[ y = -2,000x + 10,000 \]

Referring to the provided options, the correct answer is:

D) y = -2,000x + 10,000