Mathematics: Tips for Solving Series Problems in Competitive Exams

Tips for Solving Series Problem 

Series: The well arranged ordered of number/letter placed in a sequence group is called series.

A special group of numbers/letters is given in the arranged order. A particular place is left blank in the series. Students are expected to choose out the correct option and fill the blank. By these questions, the motive is to check out the ability of candidates to calculate fastly. It is also examined that how fastly a candidate establishes relationship among given elements of the series.

The questions asked from this chapter can be classified in three groups:

1. Number Series
2. Alphabet Series
3. Letter Series

1. Number Series: In number series, the given series can be based on sum, subtraction, multiplication, division, square, square root, cube, cube root etc.,

While solving the questions based on number series, these following points should always be kept in mind.

• ( i ) If the number of the given series are increasing equally, then definitely addition is taking place there.
• ( ii ) If the number of the given series decreases consecutively, then definitely subtraction is taking place there.
• ( iii ) If the number of the given series increases rapidly, then multiplication is in action there.
• ( iv ) If the number of the given series decreases rapidly, then definitely division is in action there.
• ( v ) If the series increases rapidly and then it decreases rapidly, then multiplication and division is taking place one by one.
• ( vi ) It is necessary to know about the 1 to 13 number cubes, 1 to 20 number squares and prime numbers.

Types of Question were asked in Number Series:

( i ) Completing the Given Series: In the question of this type a special place in the series is left blank and students have to fill the appropriate option in the blank by finding out the order of the numbers of series.

( ii ) Picking the Wrong Element out of the Series: In the question of this type, a series is given of which one element is placed wrong. Students have to choose out the wrong element from the series.

2. Alphabet Series: In this type of series, a series consisting of letters of alphabet is given. One or two letters of the series kept hidden and that place becomes blank or it is denoted by " ? ". Students have to fill up the appropriate letter from the options by observing the series carefully.

3. Letter Series: In letter Series, a set of letters is written four or five times with blank spaces in between. The series follows a specific pattern and the candidate is required to find out the letters which should come in place of the blank spaces.

Sample Problem: 

1) Which of the following number of the given options will come in place of question in the series ?

            1, 8, 27, 64, ?

Solution: The series is increased by 1³, 2³, 3³, 4³..........

Hence, the next number will be 5³ or 125.

2) In the series given below, only one element is wrong, find the wrong element.

(a) 3     (b) 5   (c) 9  (d) 11

Solution: The series consists of consecutive prime numbers. But the element 9 is wrong in the series because 9 is not a prime number.

3) In the following question, a series of letters has been given, a letter has been kept hidden. Find the appropriate letter from the given options by studying the series carefully.

           A, C, F, H, ?, M

Solution: In the series, the first letter increases by 2 places, while the second letter increases by 3 places and this is repeated further.

    H + 3 places = K.

4) In the series given below some of the letters are missing which are given in that order as one of the alternative below it.

a_bbc_aab_cca_bbcc

Solution: In the series, the pattern aabbcc is repeated. Hence, the series is

aabbccaabbccaabbcc