who was the youngest pres?

Theodore Roosevelt

If you look at the date of inaguration, then it would be TR. If you use the date of election, it would be JFK. Look carefully!

The youngest president of the United States was Theodore Roosevelt, who took office at the age of 42. If you want to find information about the youngest president, you can search online using search engines like Google. Simply type in "youngest president of the United States" and you'll be able to access various sources that provide information about Theodore Roosevelt and his presidency.