Question

A 12 inch-candle burns at a linear rate. It measures 11 inches two hours after it was lit. Which equation can be used to find the length of the candle, y, in inches after x hours it was lit?

Answer 1

The first step to determine the expression is to calculate the rate at which the candle burns. This is done by using the two known points, at the start the candle has 12 inches, after 2 hours it has 11 inches. So we have:

`\begin{gathered} m=(11-12)/(2) \\ m=-(1)/(2) \end{gathered}`

This means that the candle is deacreasing at a rate of 1/2 in per hour. The initial height of the candle is 12 inches, therefore we can create the following expression:

`y(x)=12-(1)/(2)x`
`y(x)=12-0.5\cdot x`