Suku ke 25 barisan bilangan 1/4,2/5,3/6,4/7.......adalah

a = 1/4
b = 2/5-1/4 
   = 3/20
U25 = 1/4 + 24(3/20)
       = 1/4 + 72/20
       = 1/4 + 18/5
        = (5 + 72)/20
      = 77/20