Let $0 < z < y < x$ be three real numbers such that $\frac{1}{ x }, \frac{1}{ y }, \frac{1}{ z }$ are in an arithmetic progression and $x$, $\sqrt{2} y, z$ are in a geometric progression. If $x y+y z$ $+z x=\frac{3}{\sqrt{2}} x y z$, then $3(x+y+z)^2$ is equal to $............$.
$150$
$140$
$130$
$120$
If $G.M. = 18$ and $A.M. = 27$, then $H.M.$ is
If $a,\,b,\;c$ are in $A.P.$ and ${a^2},\;{b^2},\;{c^2}$ are in $H.P.$, then
If $x, y, z \in R^+$ such that $x + y + z = 4$, then maximum possible value of $xyz^2$ is -
If first three terms of sequence $\frac{1}{{16}},a,b,\frac{1}{6}$ are in geometric series and last three terms are in harmonic series, then the value of $a$ and $b$ will be
If $A$ and $G$ are arithmetic and geometric means and ${x^2} - 2Ax + {G^2} = 0$, then