(16) A person has deposited $25000 in an investment which yields 14% simple interest annually. Do these amounts (principal + interest) form an A.P? If so, determine the amount of investment after 20 years.

Solution:
Simple interest = PNR/100
                     = (25000 x 1 x 14)/100
                     = 3500
Amount = principal + interest
         = 25000 + 3500
        = 28500
Amount at the end of the first year = 28500
Amount at the end of second year = 28500 + 3500
                                                   = 32000
Amount at the end of third year = 32000 + 3500
                                              = 35500
28500,32000,35500.,………………….
This is the arithmetic sequence. To find the amount of investment after 20 years we need to find 20th term
tn = a +(n - 1) d
a = 28500 d = 32000 – 28500
                   = 3500
t20 = 28500 + (20 - 1) 3500
  = 28500 + 19 (3500)
  = 28500 + 66500

  = 95000