Yes. Their sum can be equal to 1 because if they have the same denominator they will add easier like 3/4 and 1/4 or 1/2 and 1/2. All of them have the same denominator and still equal 1
The number could have been 8.699999999 so yeah there
To find the circumference of this circle, you need to use the formula C=2(3.14)r
which means circumference=2 times pi times the radius so, you would multiply 2.8(the radius of your circle) times 2. Then you would multiply that times 3.14(pi rounded to the nearest hundredth). And there u go. U have ur answer.
C=2(2.8)(3.14)
C= 5.6(3.14)
C=17.584
C=17.58 feet