When x is subracted from each of 43, 38, 11 and 10, then the numbers so obtained in this order are in proportion. What is the mean proportional between (11x + 3) and (9x - 2)?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 30.
Formula used:
If c is the mean proportion of a and b then c = √ab ---- (1)
Calculations:
⇒ (43 - x)/(38 - x) = (11 - x)/(10 - x)
⇒ (43 - x)(10 - x) = (11 - x)(38 - x)
⇒ 430 - 53x - x2 = 418 + x2 - 49x
⇒ 12 = 4x
⇒ x = 3
Now, using equation (1), we get
⇒ Mean proportion = √(11x + 3)(9x - 2) = √(36 × 25)
⇒ 30