If (x + 6), (x + 12), (x - 2), and (x + 2) are in proportion then the mean proportional between x and (x - 10) is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 12
If (x + 6), (x + 12), (x - 2), and (x + 2) are in proportion then,
(x + 6)(x + 2) = (x + 12)(x - 2)
x2 + 8x + 12 = x2 + 10x - 24
⇒ 2x = 36, x = 18
mean proportional between x and (x - 10) is:
√ (x)(x - 10)
⇒ √ 18 × 8 = √ 144 = 12