In the series,
6 4 1 2 2 8 7 4 2 1 5 3 8 6 2 1 7 1 4 3 1 2 8 6
How many pairs of successive numbers have a difference of 2 each?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Six
Successive numbers are neighbours in the series. Going from left to right, the difference of every neighbouring pair is found; the pairs whose difference is 2 (either way) are:
6, 4 (1st and 2nd numbers)
4, 2 (8th and 9th)
5, 3 (11th and 12th)
8, 6 (13th and 14th)
3, 1 (20th and 21st)
8, 6 (23rd and 24th)
So there are six such pairs. Every other neighbouring pair differs by 0, 1, 3, 4, 5 or 6.
Tip: Move along the series once and mark each pair as you meet it; a pair like 1, 2 or 2, 1 differs by 1, and looking for both orders (6, 4 and 4, 6) avoids missing a pair.