SOLUTION: 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 a slope of -0.5. See

Question 1154557: 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 a slope of -0.5. See the figure below.
Suppose that the height of the candle after 18 hours is 15 centimeters. What was the height of the candle after 15 hours?
Found 4 solutions by Alan3354, josmiceli, ikleyn, josgarithmetic:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
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 a slope of -0.5. See the figure below.
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No figure.
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Suppose that the height of the candle after 18 hours is 15 centimeters. What was the height of the candle after 15 hours?
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The slope is cm/hr = -0.5
3 hours earlier it was 3*0.5 taller
---> 15 + 1.5 = 16.5 cm
Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!

You are given the point:
( 18, 15 )

The equation is:

----------------------------
After 15 hrs:

'--------------------
check:
( 18,15 )

OK
Answer by ikleyn(52832)   (Show Source): You can put this solution on YOUR website!
.

            In his solution, @josmicely made several errors on the way.

            His check is FALSE, also, and is not "the check", at all.

            For correct solution see the post by Alan.

The correct answer is

after 15 hours, the height of the candle was 16.5 cm.

It is clear practically without calculations.

In 3 hours between 15 hours and 18 hours, the height of the candle decreases by 0.5*3 = 1.5 cm.

Therefore, at the 15 hours time moment, the height of the candle was 15 + 1.5 = 16.5 cm.     ANSWER

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@josmicely, please do not consider my post as a trial to make a war with you.

Simply, at this forum we should have a protection service for visitors from errors of tutors ---

so, I perform this protection service . . . from time to time . . .

Answer by josgarithmetic(39623)   (Show Source): You can put this solution on YOUR website!
Height y depends on time x.

Slope , and point (18,15);
Equation in point-slope form is ,

The question asks for y if x is 15.
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