math
posted by afo .
2. Mrs. young has her 18 students seated in a circle. They are evenly
spaced and numbered in order. which student is directly opposite these three students?
.student#1?
.student#5?
.student#18?

Draw a picture and figure it out. Put students at 20 degree increments around the circle. The largest number minus the smallest, across from each other, must equal 9.

#1=9
#5=12
#18=8 
Just another thought.
N = number of students equally spaced around the circle and numbered sequentially.
The student number opposite a given student number is defined by Sopp = Sg +/ N/2 depending on whether the given student number is less/more tan N/2.
The student opposite student #1 = 1 + 18/2 = #10.
The student opposite student #5 = 5 + 18/2 = #14.
The student opposite student #18 is 18  18/2 = 9. 
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