How many '7's are preceded by 9 and followed by 6 in the given series?
7, 8, 9, 7, 6, 5, 3, 4, 2, 8, 9, 7, 2, 4, 5, 9, 2, 9, 7, 6, 4, 7
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 2
A 7 is counted only when the number just before it is 9 and the number just after it is 6. Each 7 in the series is checked with its two neighbours:
1st 7 (the first term): nothing before it, not counted
9, 7, 6 (4th term): counted
9, 7, 2 (12th term): followed by 2, not counted
9, 7, 6 (19th term): counted
4, 7 (the last term): preceded by 4, not counted
Only two 7s have 9 before them and 6 after them.