Question

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 aslope of -0.6. See the figure below.Suppose that the height of the candle after 18 hours is 11.2 centimeters. What will be the height of the candle after 21 hours?

Answer 1

SOLUTION:

Recall that slope is;

$m\text{ = }\frac{y_2-y_1}{x_2-x_1}$$\frac{y_2-11.2_{}}{21_{}-18_{}}\text{ = -0.6}$

$\frac{y_2-11.2_{}}{3_{}}\text{ = -0.6}$$\begin{gathered} y_2\text{ - 11.2 = 3(-0.6)} \\ y_2\text{ - 11.2 = -1.8} \\ y_2\text{ = -1.8 + 11.2} \\ y_2\text{ = 9.4} \end{gathered}$

The height of the candle after 21 hours is going to be 9.2 centimeters.