Verified answer

12 inches = 1 foot so when you divide 840 by 12, you get 70

So...There are 70 feet in the perimeter

Look in the back of the text book it might have the answer. Does it say how big Mr.Yangs classroom is? If it was ex.60 inches then you would go 840 x 60. (You would mulitiply 840 by how big Mr.Yangs classroom is.

Since there are 12 inches in a foot, do 840 divided by 12 and that is your answer.