How many 7’s are there in the following series which are preceded by 6 which is not preceded by 8?
8 7 6 7 8 6 7 5 6 7 9 7 6 1 6 7 7 6 8 8 6 9 7 6 8 7
Answer: D
Correct answer: None of these
Each 7 that has a 6 before it must be checked for what precedes that 6. Working through the row, every such 6 turns out to have an 8 before it, or the 7 has no 6 before it at all - so the count is not one of the figures offered, and the answer is none of these.
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