posted by shannon .
Suppose that the height (in centimeters) of a candle is a linear function of the amount of time (in hours) it has been burning. After hours of burning, a candle has a height of centimeters. After hours of burning, its height is centimeters. What is the height of the candle after hours?
If the two heights are h1, and h2 after n hours, the height is
h(t) = h1 - (h1-h2)/n t
Just plug in all those missing numbers that were not in your post.
The burn rate is the height difference divided by how long it took to burn away.