Square A′B′C′D′ is the image of square ABCD under a dilation from center O1 by scale factor r . Square A′′B′′C′′D′′ is the image of square A′B′C′D′ under a dilation from center O2 by scale factor 14 . The side lengths of square A′′B′′C′′D′′ are 18 of the corresponding side lengths of square ABCD . What is the scale factor r ?
