# Short Aptitude Tutorial: Topic: Number Series; Type: Combined Series

Dear Reader, Number series is an important topic in exams. For example, in the recent bank exams, there was more than one question from this topic. In word problems (from Age, Profit & Loss, etc.,) you have to understand the problems before solving. But in number series problems, you can directly start cracking the pattern of the series and arrive at the answer.

Today we will see a twisted type of question where more than one series will be interleaved. Consider the below question.

Find the number in place of the question mark
121, 49, 144, 64, 169, ?

Let us now solve the above question.

If you observe the numbers, you can quickly find that every term is a perfect square. (For government exams, it is useful to remember squares of numbers up to 50)

However, you will face difficulty if you try to figure out the relationship between adjacent terms.

In such cases, you have to check if two series are combined. Let us separate the terms in odd places (1st, 3rd, and 5th) and even places (2nd and 4th).

Series I: 121, 144, 169
Series II: 49, 64

The first series can be simplified as 112,122,132 While the second series can be written as 72,82

The missing number is at the 6th position. Hence it should be a part of the Series II. The next number in Series II is 92 = 81