Homework Help: alisha

Posted by Anonymous on Tuesday, October 21, 2008 at 6:42pm.

a candle is a foot tall after burning an hour. after 4 h it is 10.5 in. tall. write a linear equation to model the height y of the candle after x hours. and how many hours will the candle be 6 inches tall??

plz explain the work .....

math - alisha, Tuesday, October 21, 2008 at 6:43pm
plz...help
alisha - Reiny, Tuesday, October 21, 2008 at 6:56pm
look at it as ordered pairs of the form
(time, height)
you are given 2 such points, namely
(1,12) and (4,10.5)

slope = (10.5+12)/(4-1)
= -1.5/3 = -.5 or =1/2

using height = m(time) + b (remember y=mx+b ?)
and using the point (1,12)
we get
12 = -(1/2)(1) + b
b = 12.5

so height = -time/2 + 12.5

you want height to be 6
6 = -time/2 + 12.5
12 = -time + 25
time = 25-12
= 13
- alisha - Anonymous, Tuesday, October 21, 2008 at 7:06pm
  thanks so so so much

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