If the mean proportional of 18 and 98 is 2A + 6, the value of A is:

Correct option is C

Given:
The mean proportional between 18 and 98 is given as 2A + 6
Formula Used:
Mean Proportional between two numbers a and b is given by = $$\sqrt {a × b}$$​​
Solution:
Mean proportional between 18 and 98 = 2A + 6
​$$\sqrt{18 \times 98} = 2A + 6 \\\sqrt{1764} = 2A + 6 \\42 = 2A + 6 \\2A = 42 - 6 = 36 \\A = \frac{36}{2} = 18$$​​