Question

When a particular number is sub-
tracted from each of 7, 9, 11 and
15, the resulting numbers are in
proportion. The number to be
subtracted is :
(1) 1
(2) 2
(3) 3
(4) 5​

Answer 1

3

let the no. to be subtracted be x

7-x/9-x = 11-x/15-x

7-x*(15-x) = 9-x*(11-x)

105-7x-15x+x² = 99-9x-11x+x²

105-22x+x² = 99-20x+x²

105-99 = (-20x + 22x) + (x² - x²)

6 = 2x + 0

2x = 6

x = 6/2 = 3