A certain number is added to each of the numbers 11, 15, 19, and 25. After addition, these numbers are in proportional. What is the number added?
Show answer & explanation
Correct answer: A
Explanation
The Correct answer is Option 1 i.e. 5.
Let x be the number added, such that
(11 + x) : (15 + x) :: (19 + x) : (25 + x)
⇒ (11 + x)/(15 + x) = (19 + x)/(25 + x)
⇒ (11 + x)(25 + x) = (19 + x)(15 + x)
⇒ 275 + 11x + 25x + x2 = 285 + 19x + 15x + x2
⇒ 275 + 36x = 285 + 34x
⇒ 36x - 34x = 285 - 275
⇒ 2x = 10
⇒ x = 5