If 144 : b :: b : 36, and b > 0. find the value of b.

Correct option is D

Given:

144 : b :: b : 36

Solution:

144 : b :: b : 36

This can be written as: $$\frac{144}{b}= \frac{b}{36}$$

144×36 = b × b

5184 = $$b^2$$

b = $$\sqrt{5184}$$

b = 72

The value of b is 72.

Thus, correct answer is (d) 72