Solve Number Series

How to Solve Number Series

Reasoning Ability is one of the most important section in any Bank Exam. In addition, one of the important as well as scoring topics in Reasoning Ability is Number Series. For upcoming bank exams like SBI PO, SBI Clerk, IBPS PO, IBPS Clerk, and other, aspirants should be proficient in Reasoning Ability to excel in the exam.

The arrangement of numbers in a certain order, and in which some numbers are placed wrongly in the series and some numbers are missing is called a number series. Based on calculating the numbers addition and subtraction candidates have to observe and find the accurate number to the series of numbers. Here we are providing some steps on how to solve number series questions.

Step 1: Screening

Candidates should first read the question carefully. Sometimes reading the question carefully can be enough for the candidate to solve the question.

Example:

1, 3, 7, 13, 21, 21, 31, ?

In this series, the terms are increasing by +2, +4, +6, +8, +10. So the next term will be increased by 12. So the next term is 31 + 12 = 43.

2, 4, 8, 16, 32, 64, ?

In this series, the terms are increasing by the multiple of 2. Therefore, the next term will be 64 * 2 = 128.

Step 2: Check the pattern Decreasing or Increasing or Alternating

Sometimes candidates fail to decipher the pattern of the series. Here they should try to find out the trend of the series by looking at the series pattern. Candidates can find it by checking the series weather it is decreasing or increasing or it is following an alternating pattern.

Example:

5, 10, 13, 26, 29, 58

Clearly, we can see that it is an increasing pattern

729, 512, 343, 216, 125

Here we can see that the series is of decreasing pattern

4, -8, 16, -32, 64, -128

This series is neither increasing nor decreasing. So clearly, it is following an alternating pattern

Step 3: Find the rate of increase or decrease if the series is of Increasing or decreasing pattern

Candidates should read the question carefully and find weather the nature of the series is increasing or decreasing. Moreover, on the basis of that, they should find the rate at which the terms are increasing or decreasing. Here some of the series patterns are discussed.

  • Based on subtraction and addition

In the series 4, 9, 14, 19, 24, 29 we can see that it is an increasing series and the rate of increase is 9-4 = 5

In the series 13, 11, 9, 7, 5 we can see that it is a decreasing series and the rate of decrease is 13-11 = 2

  • Based on division and multiplication

In the series 4, 8, 16, 32, 64, we can see that it is an increasing series and the series is increasing by the multiple of 2.

In the series 100, 50, 25, 5, 1 we can see that it is a decreasing series and the series is decreasing as the terms are divided by 5.

  • Based on square and cube

In the series 8, 27, 125, 343, 1331, 2197 we can see that it is an increasing series. The series is the cube of the consecutive prime numbers from 2 to 13.

Step 4: Check if the series is alternating

For alternating series, candidates need to check whether the series has two different operations, which are being alternately performed, or there is a mix of two series.

Example:

In the series 4, 9 6, 18, 9, 27, 13, 36. This series is a mix of two series 9, 18, 27, 36 and 4, 6, 9, 13.

In the series 200, 600, 1200, 1600, 3200, 3600, 7200 two types of operations are going, one is the addition of 400 and the second is multiplication by 2.

With lots of practice, these steps can help the candidates to build the intuition that is required to solve number series problems.