Identify the missing number within the series.
86, ?, 79, 75, 72, 68
Answer: A
Explanation: The difference between the numbers in this series alternates between -4 and -3. The second number in the series is therefore 82.
98, 94, ?, 70, 38
Answer: C
Explanation: The difference between the numbers in this series increases by -4, -8, -16, -32. The third number in the series is therefore 86.
11, 19, ?, 41, 55
Answer: B
Explanation: The difference between the numbers in this series increases by 2 each time – 8,10,12, 14. The third number in the series is therefore 29.
33, ?, 19, 12, 5
Answer : B
Explanation: The numbers in this series decrease by 7 each time. Therefore the second number is 26.
Identify the missing number at the end of the series:
662, 645, 624, 599, ?
Answer : E
Explanation: The difference between the numbers in this series increases by -4 each time: -17,- 21,-25, etc. This will produce a difference of -29 between 599 and the next number in the series, which is therefore 570.
