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posted by Sheenybeany on .
Point Q is the image of point P under a dilation with center O and scale factor 4. If PQ = 18, then what is OP?

all distances also scale by a factor of 4.

Sorry, but that's not right :(
I really need to do this. Any help? 
what do you mean by "that's not right?" What calculation did you do?
Without loss of generality, we can take the distances to be measured along the xaxis.
We have two points, P and Q on the xaxis, where
OQ = 4(OP) because of the dilation.
Since PQ=18, that means that 3/4 of the distance OQ = 18.
So, OQ = 24 and OP = 6.
All because the distances grew by a factor of 4, as I said. 
Like I said, the answer is wrong! I put it into my online class and it said it was 6. Thanks a whole bunch, Steve.