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counting and probability junior
Problem
Eight points are spaced around at intervals of one unit around a square, as shown. Two of the points are chosen at random. What is the probability that the two points are one unit apart? 
(A)
(B)
(C)
(D)
Solution
The two points are one unit apart at places around the edge of the square. There are ways to choose two points. The probability is
Final answer
B