It takes 20 men 6 hours to seed 40 acres of land. so how many hours would it take for 10 men to seed 90 acres of land?

i would say true? if the unit was informational and it "refreshed your understanding", then true.

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.