Quantitative Aptitude: Series

Type 1: Prime number series
Find out the next term or ? in the given series
Ex. 1. 7,11,13, 17, 19,.....?
Ex. 2. 3, 7, 13, 19,...........?
Ex. 3. 3, 7, 17, 31,...........?
Solutions

1. Given series is a consecutive prime number series, therefore next term will be 23
2. 3, 5, 7, 11, 13, 17, 19, 23
3. 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53

Type 2: Addition Series

The series, in which next term is obtained by adding a specific number or previous term.

Ex. 1. 11, 25, 39, 53, 67 ..............?

Ex. 2. 4, 7, 11, 18, 29, .................?

Solutions

1. Every next term is obtained by adding +14 to the previous term.                                                   Required term = 67 + 14 = 81
2. Next term is obtained by adding previous two term = 18 + 29 = 47.

Type 3: Multiple Series

When each term of a series is obtained by multiplying a number with previous term.

Ex. 1. 3, 3, 6, 18, 72, ................?

Ex. 2. 7, 8, 18, 57, ....................?

Solutions

1.  x1, x2, x3, ..................    i.e. Required term = 72 x 5 = 360
2.  x1+1, x2+2, x3+3, x4+4  i.e. Required term  57 x 4 + 4 = 232

Type 4: Alternative Series
(a) it is a combination of two different series
(b) Two different operation are performed on successive term alternately.
Ex. 1. 15, 14, 19, 11, 23, 8 ........?
Ex. 2. 50, 200, 100, 100, 200, 50, 400, ................?
Solutions

1. First Series 15, 19, 23, .............?   2nd series 14, 11, 8  i.e. Required term
2. First Series 50, 100, 200, 400       2nd series 200, 100, 50, 25   Required term

Type 5: Some Important Series

Ex. 1. 2, 3, 6, 15, 45 ........?

Ex. 2. 2, 3.5, 8, 21.5, 66.5 .........?

Ex. 3. 50, 60, 75, 97.5, .........?. 184. 275

Solutions

1. 2 x 1.5, 3 x 2, 6 x 2.5, 15 x 3     i.e. Required term = 45 x 3.5 = 157.5
2. 2 x1.5 + 0.5,  3.5 x 2 + 1, 8 x 2.5 + 1.5, 21.5 x 3 + 2, 66.5 x 3.5 + 2.5 = 235.25    i.e. Required term = 235.25
3. 50 x 1.2 = 60, 60 x 1.25 = 75,  75 x 1.3 = 97.5,  97.5 x 1.35 = 131.625     Required term = 131.625

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