we are given the arithmetic series 2, 1 3/5, 1 1/5.. In this case, the arithmetic difference is -2/5 by taking the difference of 2 and 1 3/5 and 1 3/5 and 1/5. The general formula of arithmetic sequence is an = a1 + d*(n-1). Substituting, an = 2 -2/5*(n-1). a25 hence is equal to a25 = 2-2/5*(25-1) = -38/5