What must be added to each of the numbers 7, 11 and 19, so that the resulting numbers may be in continued proportion? Select
A) 3	B) 5	C) 4	D) -3	E) -2
Let X be the required number, then   (7 + X) : (11 + X) :: (11 +X) : (19 + X)   (7 + X) (19 + X) = (11 + X)2   X2 + 26X + 133 = X2 + 22X + 121   4X = - 12 or X = - 3   ANSWER:-3
<result>D</result>
What must be added to each of the numbers 7, 11 and 19, so that the resulting numbers may be in continued proportion?