SOLUTION: Can you help me with this word problem that I am struggling with? The distance D between a fixed spring and the floor is a linear function of the weight w attached to the bottom o

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Question 2465: Can you help me with this word problem that I am struggling with?
The distance D between a fixed spring and the floor is a linear function of the weight w attached to the bottom of the spring. The spring is 12 inches from the floor when the weight is 2 grams, and the spring is 7 inches from the floor when the weight is 4 grams. Write D as a linear function of w.

Answer by khwang(438) About Me  (Show Source):
You can put this solution on YOUR website!
Let D = aW +b,
when W = 2, D = 12, so 12 = 2a + b...(1)
when W = 4, D = 7, so 7 = 4a + b...(2)
(2)-(1): 2a = -5, or a = -2.5,
hence b = 12+ 2*2.5 = 17.
Answer: D = -2.5W + 17.
Kenny