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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 5 hours of burning, a candle has a height of 21.5 centimeters. After 21 hours of burning, its height is 16.7 centimeters. What is the height of the candle after 15 hours?

Sagot :

Answer:

The height is 18.5cm

Step-by-step explanation:

Given

Let

[tex]y =height[/tex]

[tex]x = time[/tex]

So, we have:

[tex](x_1,y_1) = (5,21.5)[/tex]

[tex](x_2,y_2) = (21,16.7)[/tex]

Required

The height after 15 hours

First, calculate the slope (m)

[tex]m = \frac{y_2 - y_1}{x_2 - x_1}[/tex]

This gives:

[tex]m = \frac{16.7-21.5}{21-5}[/tex]

[tex]m = \frac{-4.8}{16}[/tex]

[tex]m = -0.3[/tex]

The linear equation is then calculated as:

[tex]y =m(x - x_1) + y_1[/tex]

Where

[tex]m = -0.3[/tex]

[tex](x_1,y_1) = (5,21.5)[/tex]

This gives:

[tex]y =-0.3(x - 5) + 21.5[/tex]

Open bracket

[tex]y =-0.3x + 1.5 + 21.5[/tex]

[tex]y =-0.3x + 23[/tex]

After 15 hours

[tex]x = 15[/tex]

[tex]y =-0.3*15 + 23[/tex]

[tex]y =-4.5 + 23[/tex]

[tex]y =18.5[/tex]

The height is 18.5cm