What number must be subtracted from each of the numbers 55, 23, 43 and 19, so that the new values are in proportion?
Answer & explanation
Correct answer: option 3
Let the required number = x,
The proportion =
(55 - x) : (23 - x) :: (43 - x) : (19 - x)
The product of middle terms = the product of extreme terms
(23 - x)(43 - x) = (55 - x)(19 - x)
989 - 66x + x² = 1045 - 74x + x²
8x = 56
x = 7
hence the required number is 7