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1/5 + 3/5 = 4/5
5 - 5/3 + 5/9 - 5/27 + ... = 5 + 5(-1/3)¹ + 5(-1/3)² + 5(-1/3)³ + ... The required sum is an infinite GP with initial term a = 5, and common difference r = -1/3 As |r| < 1, the sum can be found from sum = a/(1 - r) → 5 - 5/3 + 5/9 - 5/27 + ... = 5/(1 - (-1/3)) = 5/(1 + 1/3) = 5/(4/3) = 5 × 3/4 = 15/4 = 3¾
The sum of -1/15 and -3/5 is -2/3
The sum of 5/6 and 5/6 is 1 2/3
1.5 or 1 + 1 over 2