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 10 hours of burning, a candle has a height of 21 centimeters. After 28 hours of burning, its height is 19.2 centimeters. What is the height of the candle after 7 hours?

Answer 1

The height of the candle after 7 hours is 21.3 centimeters.

Explanation:

From the information given you can assign the following values:

x1=10; y1=21

x2=28; y2=19.2

First, you have to find the slope using the following formula:

m=
`(y2-y1)/(x2-x1)`

m=
`(19.2-21)/(28-10)`

m=-0.1

Then, you can find the equation using the point/slope formula:

y-y1=m(x-x1)

y-21=-0.1(x-10)

y-21=-0.1x+1

y=-0.1x+22

Finally, to find the answer you need to replace the value of x that would be 7 in y=-0.1x+22:

y=-0.1(7)+22

y=-0.7+22

y=21.3

According to this, the height of the candle after 7 hours is 21.3 centimeters.