Question

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 14 hours of burning, a candle has a height of 27.6 centimeters. After 31 hours of burning, its height is 25.9 centimeters. What is the height of the candle after 21 hours?

Answer 1

From the anaysis of the burning candle in the question, we are asked to find the height of the candle after 21 hours.

14 hours ---------> 27.6 cm

31 hours ----------> 25.9cm

21 hours -----------> x cm

31 - 14/21 - 14 = 25.9 - 27.6/x - 27.6

17/7 = -1.7/x - 27.6

17(x - 27.6) = 7(-1.7)

17x - 469.2 = -11.9

17x = -11.9 + 469.2

17x = 457.3

Divide both sides by 17:

17x/17 = 457.3/17

x = 457.3/17

x = 26.9 cm

Therrfore, the height of the candle after 21 hours is 26.9 cm.