SOLUTION: The height (in centimeters) of a candle is a linear function of the amount of time (in hours) it has been burning. When graphed, the function gives a line with a slope of &#8722;0.

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Question 929132: The height (in centimeters) of a candle is a linear function of the amount of time (in hours) it has been burning. When graphed, the function gives a line with a slope of −0.3. See the figure below.
http://i.gyazo.com/edc311720eb8262dac67f4dcc2eb3f86.png
Suppose that the height of the candle after 15 hours is 24.5 centimeters. What was the height of the candle after 8 hours?
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I get that the question is asking for 8 hours after the start of the burning, not 23 hours, but I just don't understand how to apply the slope here.
Answer by josgarithmetic(39617) (Show Source):
You can put this solution on YOUR website!
The quick way through is to know the slope-intercept form for a linear equation. Look at the graph showing x=0, y=b, the y-intercept. You don't know it, but at least you are given the slope and one data point.

substitute the known given point.

The equation for your line is

Just find y for x=8.

SOLUTION: The height (in centimeters) of a candle is a linear function of the amount of time (in hours) it has been burning. When graphed, the function gives a line with a slope of &#8722;0.

SOLUTION: The height (in centimeters) of a candle is a linear function of the amount of time (in hours) it has been burning. When graphed, the function gives a line with a slope of −0.