I am trying some quantitative aptitude questions and I am unable to solve this particular multiple-choice finish-the-sequence question:

Find the missing number in the sequence: 61, 52, 63, 94, __, 18, 001, 121

Options: A) 46, B) 70, C) 66, D) 44.

Unfortunately, I have no clue how it can be solved; I don't even know where to start. However, I know the answer is:


Please help.

  • $\begingroup$ FYI - the more pattern-recognition questions like this you find in an aptitude test, the more sure you can be that it is a low-quality test whose results are meaningless. On other forums, one can find posts about finding reasonable justifications of all offered solutions for the missing entry. Usually a reasonable justification for choosing any of them can be found. Highly intelligent people can often spot two or three possible answers and have to arrive at the desired one by guessing the most likely reasoning of the author. $\endgroup$ Jun 22, 2020 at 17:39

1 Answer 1


Try looking at this another way round. Specifically:

Read all the numbers backwards, i.e. taking the right-hand digits first. Your sequence is then: 16, 25, 36, 49, ___, 81, 100, 121. What are these?

The answer is beneath this spoiler - but try to solve it yourself first before you look. You see, all of these are:

Square numbers from 4 squared up to 11 squared. The missing number is thus 8 squared (64), so reverse its digits to get 46, your final answer.

The giveaway is:

the number '001' - why does this have leading zeros when none of the others do? Reverse it and all becomes obvious!


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