If $a, b, c$ are positive integers,then $(a + b)(b + c)(c + a)$ is

If the geometric mean between two numbers is $4$ and the arithmetic mean is $5$,then the harmonic mean is .......

If $A.M.$ and $G.M.$ of $x$ and $y$ are in the ratio $p : q$,then $x : y$ is

For two positive numbers $a$ and $b$,if $a, b$ and $\frac{1}{18}$ are in a geometric progression,while $\frac{1}{a}, 10$ and $\frac{1}{b}$ are in an arithmetic progression,then $16a + 12b$ is equal to $.........$.

If the ratio of $A.M.$ between two positive real numbers $a$ and $b$ to their $H.M.$ is $m:n$,then $a:b$ is

The sum of three decreasing numbers in $A.P.$ is $27$. If $-1, -1, 3$ are added to them respectively,the resulting series is in $G.P.$ The numbers are