Question

If x is a positive number and the geometric mean of 9 and 16, find the value of x?

• A. 3
• B. 4
• C. 12
• D. 25

Answer 1

The correct option is C 12

x is the geometric mean of 9 and 16. Then we have $9:x::x:16$ are in proportion

$\therefore$ $x^2=9\times 16=144x=\sqrt{144}x=\pm 12$

As it is given x is a positive number, geometric mean of 9 and 16 is 12.