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Question 26581: Hi, I desperately need your help with this linear word problem, I have been working on it for the past few days, it is as follows:
Due to increased sensitivity to the suffering of animals, the number of animals used in laboratory experiments is being reduced. In 1984 about 200 thousand dogs were used in labrotory experiments in the US. Since then, the number of dogs used in laboratory experiments has decreased by about 10 thousand dogs per year. Let d represent the number of dogs (in thousands) used in laboratory experiments in the US at t years since 1984.
I have been trying to figure out the equation that expresses the number of dogs(in thousands) d used in laboratory experiments in terms of the years t since 1984. I need this equation to determine how many dogs were used in laboratory experiments in the year 2003.(I would know how to find the answer to that if I could get to the right equation for the problem.)My instructor told the class that when you see "decreased by about 10 thousand dog PER year", that would be the slope and because it says decreased its negitve. So, this is what I got and i really dont think its right... d = -10 t dont i need a y intercept?
PLEASE HELP! THANK YOU SO VERY MUCH!!
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! the gradient is -10 yes, so we have an equation of the form y=mx+c. So we get d=-10t+c.
What is c? Well to find it, we need to know a set of (t,d), which we do...at t=0, d=200 (thousand).
so, 200 = -10(0) + c
--> c = 200
so equation is d = -10t + 200
As t increases, so the value of d falls from a maximum value of 200.
Jon
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