SOLUTION: Given that a candle is 13.5 inches tall when it has been burning for 8 hours at a rate of 0.5 inches per hour, How tall was the candle when it had been burning for 2.5 hours?

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Question 1048202: Given that a candle is 13.5 inches tall when it has been burning for 8 hours at a rate of 0.5 inches per hour,
How tall was the candle when it had been burning for 2.5 hours?
Found 2 solutions by Alan3354, Edwin McCravy:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Given that a candle is 13.5 inches tall when it has been burning for 8 hours at a rate of 0.5 inches per hour,
How tall was the candle when it had been burning for 2.5 hours?
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It's 5.5 hours less burning time (8 - 2.5)
5.5*0.5 = 2.75 inches taller.
13.5 + 2.75 = 16.25 inches

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!

a candle is 13.5 inches tall when it has been burning for 8 hours 
So when the time = 8 hours, the 
candle's height = 13.5 inches

burning...at a rate of 0.5 inches per hour, 
So when the time = 9 hours, the candle's height 
will be 13 inches.

Let x = the number of hours the candle has been 
burning

Let y = the height of the candle when it has been 
burning for x hours.

So when x = 8, y = 13.5 and
when x = 9, y = 13

We want to find the equation of the line that passes
through the two points (8,13.5) and (9,13)
 
First we use the slope formula

m%22%22=%22%22%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29
where (x1,y1) = (8,13.5)
and where (x2,y2) = (9,13)

m%22%22=%22%22%2813-13.5%29%2F%289-8%29%22%22=%22%22%28-0.5%29%2F1%22%22=%22%22-0.5%29

Point-slope formula:
y - y1 = m(x - x1)
where (x1,y1) = (8,13.5)

y - 13.5 = -0.5(x - 8)

y - 13.5 = -0.5x + 4

       y = -0.5x + 17.5

How tall was the candle when it had been burning
for 2.5 hours?
Substitute 2.5 for x

       y = -0.5(2.5) + 17.5
       y = 16.25

So the candle was 16.25 inches tall when it had been 
burning for only 2.5 hours.

Edwin