At the beginning of part3, Meno asks Socrates to return to the original question that whether virtue can or cannot be taught, without knowing what virtue is, Socrates sets up hypothesis about triangular space and circle to account for the properties of virtue. After explanation, the conclusion that Socrates makes is that virtue is kind of knowledge and must be taught.

In the same way with regard to our question about virtue, since we do not know either what it is or what kind of thing it may be, we had best make use of a hypothesis in considering whether it can be taught or not, as thus: what kind of thing must virtue be in the class of mental properties, so as to be teachable or not? In the first place, if it is something dissimilar or similar to knowledge, is it taught or not—or, as we were saying just now, remembered? Let us have no disputing about the choice of a name: is it taught? Or is not this fact plain to everyone—that the one and only thing taught to men is knowledge?
Meno
I agree to that.
Socrates
Then if virtue is a kind of knowledge, clearly it must be taught?
Meno
Certainly.

when they discuss the relationship between virtue and knowledge，Socrates also mentions that this hypothesis or opinion stands in the idea that virtue is a good thing and is profitable.Then，Socrates consider the goods of the soul and takes some examples such as courage to lead to the wisdom（virtue must be a sort of wisdom）

Socrates
No, for then, I presume, we should have had this result: if good men were so by nature, we surely should have had men able to discern who of the young were good by nature, and on their pointing them out we should have taken them over and kept them safe in the citadel, having set our mark on them far rather than on our gold treasure, in order that none might have tampered with them, and that when they came to be of age, they might be useful to their country.
Meno
Yes, most likely, Socrates.
Socrates
So since it is not by nature that the good become good, is it by education?
Meno
We must now conclude, I think, that it is; and plainly, Socrates, on our hypothesis that virtue is knowledge, it must be taught.

Ultimately，they conclude that all beneficial things are good if they are accompanied by knowledge or wisdom，and because virtue is good，is a kind of knowledge，therefore virtue can be taught. Overall，I just assert that this kind of conclusion is not convincing，and I just dont know how to admit wisdom is the same thing as virtue. All the other things maybe are so so.

Later，they begin to suspect that whether virtue is a kind of knowledge. So a new topic has appeared “are there no teachers of virtue？”In order to criticize Menos conclusion， Socrates just invites Anytus joining into the conversation. Through this process，they take some instances about the situation that how do some famous person teach their kids.

Socrates
And, you know as well as I, he taught them to be the foremost horsemen of Athens, and trained them to excel in music and gymnastics and all else that comes under the head of the arts; and with all that, had he no desire to make them good men? He wished to, I imagine, but presumably it is not a thing one can be taught. And that you may not suppose it was only a few of the meanest sort of Athenians who failed in this matter, let me remind you that Thucydides’27 also brought up two sons, Melesias and Stephanus, and that besides giving them a good general education he made them the best wrestlers in Athens: one he placed with Xanthias, and the other with Eudorus—masters who, I should think, had the name of being the best exponents of the art. You remember them, do you not?
Anytus
Yes, by hearsay.
Socrates
Well, is it not obvious that this father would never have spent his money on having his children taught all those things, and then have omitted to teach them at no expense the others that would have made them good men, if virtue was to be taught? Will you say that perhaps Thucydides was one of the meaner sort, and had no great number of friends among the Athenians and allies? He, who was of a great house and had much influence in our city and all over Greece, so that if virtue were to be taught he would have found out the man who was likely to make his sons good, whether one of our own people or a foreigner, were he himself too busy owing to the cares of state! Ah no, my dear Anytus, it looks as though virtue were not a teachable thing.

The results are all same that they didnt teach their sons to be virtuous as themselves，which reveal that it has no this kind of teacher to teach the virtue.