In the following series, which letter occupies the 1000th position? ABCD......XYZ YX....BA BCD.....YZ YX....CBA BC.....YZ.......
B
We have 3 patterns:
I. ABCD . XYZ.Which occurs only once
II. YX BA, which repeats alternately
III. BC .. YZ, which repeats alternately
Now, I has 26 terms
So, number of terms before the desired term = (999 -- 26 ) = 973
Each of the patterns which occurs after I, has 25 letters
Now, 973 ÷ 25 gives quotient = 38 and remainder = 23
Thus, the 1000th term of the given series is the 24th term of the 38th pattern after I which is B.