How many states must ratify an amendement for it to become part of the constitution?

2/3 of both houses

The above is incorrect. For an amendment to become part of the Constitution it must be ratified by 3/4th's of the States. With 50 states, this means 38 states must ratify and accept the amendment--this can take years and some amendments have never been ratified. It does take 2/3rd's of both houses of Congress to pass an amendment before it goes to the states to be ratified.