If x is added to each of 10, 16, 22 and 32, the numbers so obtained in this order are in proportion. What is the mean proportional between the numbers (x + 1) and (3x + 1)?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e 15
Explanation:
If x is added to each of numbers, the numbers so obtained in this order are in proportion
so, (10 + x)/(16 + x) = (22 + x)/(32 + x)
(10 + x)(32 + x) = (16 + x)(22 + x)
320 + 10x + 32x + x2 = 352 + 16x + 22x + x2
320 + 42x = 352 + 38x
4x = 32
x = 8
(x + 1) = 8 + 1 = 9
(3x + 1) = 24 + 1 = 25
Mean proportional = √(9 × 25) = 15