@Power_Ranger......I am glad you have the spirit of inquiry. One must possess this quality to understand life. Now, you asked why Rama didn't understand Vasistha's silence answer. Will a 4th grader understand E = MC^2? Absolutely not because the 4th grader don't have the faculty to understand Einstein's equation. He must wait many years and work hard in order to understand this great equation. Similarly, Rama was not in a position to understand Vasistha's answer because he lacked the direct experience of inner silence and couldn't decipher the meaning behind Vasistha's silence. In other words, true knowledge only comes through direct experience which Rama didn't have; and,Rama thought all questions could be answered through the help of verbal language which is not true. This was the field where the knower and the known merge together. There is no subject-object relationship here. When the knower and the known merge together, who knows what? When this happens, contentment spontaneously arises and there is deep silence which is real.