A candle is lit and burns and the length of the candle changes at a constant rate of -1.5 inches per hour. 2 hours after the candle was lit the candle is 8.2 inches long.

Write a formula that expresses the remaining length of the candle in inches, L, in terms of the number of hours t that have elapsed since the candle was lit.

Respuesta :

Answer:

[tex] L = -1.5 \frac{in}{hr} t + 11.2[/tex]

Step-by-step explanation:

For this case we need to define some notation:

[tex] L[/tex] represent the remaining length of the candle in inches

[tex] t[/tex] represent the time in hours that have elapsed since the candle was lit.

For this case we assume that L and f are related so then we can write this like that: [tex] L =f(t)[/tex] L is a function of t.

And for this case we have a constant rate given of:

[tex] m = \frac{\Delta L}{\Delta t}= -1.5 \frac{in}{hr}[/tex]

And we know a initial condition [tex] L(2) = 8.2 in[/tex]

So then since we have a constant rate of change we can use a linear model given by:

[tex] L = m t +b[/tex]

Where m is given and we need to find b. If we use the initial condition we have this:

[tex] 8.2 = -1.5 \frac{in}{hr} (2) +b[/tex]

And solving for b we got:

[tex] b = 8.2 +1.5*2=11.2 in[/tex]

So then our lineal model would be given by:

[tex] L = -1.5 \frac{in}{hr} t + 11.2[/tex]

The remaining length of the candle in inches, L after t hours is given by L = -1.5t + 11.2

Linear equation

A linear equation is in the form:

y = mx + b

where y, x are variables, m is the rate of change and b is the initial value of y.

Let L represent the length of the candle in hours after t hours.

The length of the candle changes at a constant rate of -1.5 inches per hour. hence:

  • m = -1.5

2 hours after the candle was lit the candle is 8.2 inches long. Hence:

  • 8.2 = -1.5(2) + b
  • b = 11.2

Hence:

L = -1.5t + 11.2

The remaining length of the candle in inches, L after t hours is given by L = -1.5t + 11.2

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