The mean proportional between 36 and a number N is three times the mean proportional between 8 and 32. The number N is:

Correct option is D

Given:
Mean proportional between 36 and N.
Three times the mean proportional between 8 and 32.
Formula Used:
Mean proportional between A and B = $$\sqrt {A\times B}$$​
Solution:
Mean proportional between 8 and 32 = √(8 × 32) = √256 = 16.
Three times the mean proportional = 3 × 16 = 48.
Mean proportional between 36 and N = 48.
√(36 × N) = 48
36 × N = 48²
36 × N = 2304
N = 2304 ÷ 36
N = 64