If the numbers 3 9 , 4 20 , 6 25 are arranged in ascending order, then the right arrangement is -

Answer: Option C

$$\text{root}3\text{of}9,\text{root}4\text{of}20,\text{root}6\text{of}25$$
Taking L.C.M of 3, 4 and 6
$$\begin{array}{rl}& =\text{root}12\text{of}{9}^4,\text{root}12\text{of}{20}^3,\text{root}12\text{of}{25}^2\\ & =\text{root}12\text{of}6561,\text{root}12\text{of}8000,\text{root}12\text{of}625\end{array}$$
So, ascending order
$$=\text{root}6\text{of}25,<\text{root}3\text{of}9,<\text{root}4\text{of}20$$