Problem 591

Find S20 for the series -1 + -3 + -5 + -7 +…   Solution:-   a1 = -1, d = -2 S20 = [2*a1 + (n-1)*d] S20 =  [2*(-1) + (20-1)*-2] S20 =…

Problem 589

  Find the 10th term of an arithmetic sequence if t1 = 2.1 and t4 = 1.83.   Solution:-   1.83 = 2.1+(4-1)d d = -0.09 n10th = 2.1+(10-1)*(-0.09) n10th = 1.29