Number series tests present numerical sequences that follow a logical rule based on elementary arithmetic. An initial sequence is presented from which the rule must be deduced. You are then asked to predict the next number that obeys the rule. The difficulty level of these questions can increase in two ways: the logic behind the sequence becomes less trivial, thereby demanding attention and creativity, or the missing number is positioned at an early stage, thus preventing you from deciphering the hidden rule by looking only at the previous numbers in the sequence.
Watch the video below for some general solving tips for number series tests. In JobTestPrep's preparation package you will find a plethora of more specific solving tips.
1. Examine the difference between adjacent numbers.
→ In a simple series, the difference between two consecutive numbers is constant.
Example: 27, 24, 21, 18, __
Rule: There is a difference of (-3) between each item. The missing number in this case is 15.
→ In a more complex series, the differences between numbers may be dynamic rather than fixed, but there is still a clear logical rule.
Example: 3, 4, 6, 9, 13, 18, __
Rule: Add 1 to the difference between two adjacent items. After the first number add 1, after the second number add 2, and after the third number add 3, etc. In this case, the missing number is 24.
2. See whether there is a multiplication or division pattern between two adjacent numbers.
Example: 64, 32, 16, 8, __
Rule: Divide each number by 2 to get the next number in the series. The missing number is 4.
3. Check whether adjacent numbers in the series change based on a logical pattern.
Example: 2, 4, 12, 48, __
Rule: Multiply the first number by 2, the second number by 3 and the third number by 4, etc. The missing item is 240.
4. See if you can find a rule that involves using two or more basic arithmetic functions (+, -, ÷, x). In the series below, the functions alternate in an orderly fashion.
Example: 5, 7, 14, 16, 32, 34, __
Rule: Add 2, multiply by 2, add 2, multiply by 2, etc. The missing item is 68. Tip: Series in this category are easy to identify. Just look for numbers that do not appear to have a set pattern.
In a series that involves two or more basic arithmetic functions, the differences between adjacent items effectively create their own series. We recommend that you try to identify each pattern separately.
Example: 4, 6, 2, 8, 3, __
Rule: In this series, the differences themselves create a series: +2, ÷3, x4, -5. The numbers advance by intervals of 1, and the arithmetic functions change in an orderly sequence. The next arithmetic function in the series should be +6, and so the next item in the series is 9 (3+6 = 9).
While it is unlikely you will take a test consisting of just number series questions, this type of question is included on many different numerical reasoning and numeracy tests. Preparing for numerical sequence questions should be part of any preparation before a numerical assessment.
JobTestPrep's practice pack teaches you how to quickly spot patterns and understand the reasoning behind them with the help of video tutorials, study guides, and practice questions.