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 11 hours of burning, a candle has a height of 16.5 centimeters. After 30 hours of burning, its height is 7 centimeters. What is the height of the candle after hours?

Answer 1

height (y) is dependent on burning time (x)

it loses 9.5 cm (16.5 - 7) over 19 hr (30 - 11)
... so the slope of the line is ... -9.5 / 19 = -1/2

y = - 1/2 x + b ... substitute one of the points to find b (the y-intercept)