Question

If the AM of two numbers is 9 and their HM is 4, then their GM is

Answer 1

For any given numbers, their means, Arithmetic mean (AM), Geometric mean, (GM) and Harmonic mean are related by the relation
$G{M}^2=AM\times HM$
So, $G{M}^2=9\times 4=36$
$=>GM=6$