Tara was 50 feet below the surface of the ocean. She then swam up 20 feet. Which integer represents the starting depth? Explain how you know.

answer: 4  

the square root of 16 is 4. it is a very simple mathematic concept. a square root when a number multiplied by itself will result in a number. here, the number 16 comes when 4 is multiplied by 4. hence the square root of 16 is 4. you can always figure out a square root by the inverse operation of squaring.