John wants to plant some flowers in a cube shaped planter box if one edge of the box measures 4 inches how much soil will be needed to fill the planter?

it is impossible.

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.