When the same number is subtracted from each of 7, 9, 11 and 15, the resulting numbers are in proportion. The number subtracted is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 3.
Let the given numbers be a, b, c, and, d
Then, a/b = c/d
let x be subtracted from each number
⇒ a = 7, b = 9, c = 11 and d = 15
⇒ (7 - x)/(9 - x) = (11 - x)/(15 - x)
⇒ (7 - x)(15 - x) = (11 - x)(9 - x)
⇒ 105 - 7x - 15x + x2 = 99 - 11x - 9x + x2
⇒ 105 - 22x = 99 - 20x
⇒ 6 = 2x
⇒ x = 3