SOLUTION: Hello my name is Suzy. I have an algebra word problem that I am having trouble with. I would appreciate any help I can get. The intensity (I) of light from a light bulb varies i

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Hello my name is Suzy. I have an algebra word problem that I am having trouble with. I would appreciate any help I can get. The intensity (I) of light from a light bulb varies i      Log On


   



Question 515272: Hello my name is Suzy. I have an algebra word problem that I am having trouble with. I would appreciate any help I can get.
The intensity (I) of light from a light bulb varies inversly as the square of the distance (d) from the light bulb. Suppose (I) is 160w/m^2 when the distance is 4m. How much farther would it be to a point where the intensity is 90w/m^2?
I know that since it is an inverse problem I use the format y=k/x and if I use the format for the problem I would use I=k/d^2.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+I+=+k%2A%281%2Fd%5E2%29+
Find k using the given data:
+I+=+160+
+d+=+4+
+160+=+k%2A%28+1%2F16%29+
+k+=+2560+
------------
If +I+=+90+
+90+=+2560%2A%281%2Fd%5E2%29+
+d%5E2+=+2560%2F90+
+d%5E2+=+256%2F9+
+d+=+16%2F3+ m
When +I+=+160+, d+=+4+,
or +12%2F3+
The point where +I+=+90+ is
+16%2F3+-+12%2F3+=+4%2F3+ m further