One type of number series that often appears in competitive exams is the alternating series.
What is Alternating number series
This type of series may consists of two series combined into a single series. The alternating terms of this series may form an independent series in itself
The alternating series are quite difficult. You need to make many examples to get acquainted and get into their spirit and be able to deal with them in the exams. Many exercises-practice will give you the confidence to succeed in the competitive exams.
Examples
Question1: Look carefully at the following series.What pair comes next?
46, 43, 40, 38, 35, 32, 30,...?,,,,,?
This is an alternating subtraction series in which 3 is subtracted twice, then 2 is subtracted once, then 3 is subtracted twice, and so on. So the next terms in the following series will be 27, 24
Question2: Look carefully at the following series.What pair comes next?
18, 8, 18, 10, 18, 12, 18, ...
In this alternating repetition series, the random number 18 is interpolated every other number into an otherwise simple addition series that increases by 2, beginning with the number 8.
12+2=14
18 is interpolated every other number
Answer is 14, 18
Question3: Look carefully at the following series.What pair comes next?
9,18,10,20,12,24,...
This is an alternating multiplication and subtracting series: First, multiply by 2 and then subtract 8.
9X2=18 18-8=10 10X2=20 20-8=12 12X2=24
So 24-8=16 16x2=32
Answer is 16, 32
Practice with selective questions
Alternating number series test
Detailed solutions
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By Panos Kalliantasis
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