When x is subtracted from each of 19, 28, 55 and 91, the numbers so obtained in this order are in proportion. What is the value of x?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 7
Let a, b, c, and d are in proportion then,
⇒ a/b = c/d ⇔ ad = bc
⇒ (19 - x)(91 - x) = (28 - x)(55 - x)
Now instead of solving this equation, we can put the values.
⇒ x = 8
⇒ (19 - 8)(91 - 8) = (28 - 8)(55 - 8)
⇒ 11 × 83 = 20 × 47 This is wrong.
⇒ x = 7
⇒ (19 - 7)(91 - 7) = (28 - 7)(55 - 7)
⇒ 12 × 84 = 19 × 48 This satisfies