Bunuel wrote:
In a certain sequence, when you subtract the Mth element from the (M-1)th element, you get twice the Mth element (M is any positive integer). What is the fourth element of this sequence?
(1) The first element of the sequence is 1.
(2) The third element of the sequence is 1/9.
Since the given rule tells us how to calculate one element in a sequence based on the one before/after it, then to know the value of the fourth element, all we need to know is the value of one of the elements.
We'll look for statements that give us this information, a Logical approach.
(1) gives us the first element and is sufficient.
(2) gives us the third element and is sufficient.
(D) is our answer.
Note that you don't actually need to calculate that the given rule is 'the Mth element is 1/3 the (M-1)th element' in order to solve the above.
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