Number series : 10 Questions from Previous Exams

Ques 1.

5 , 15 , 30 , 135, 405, 1215, 3645

(a) 3645

(b) 5

(c) 405

(d) 1215

(e) 30

Ques 2.

2, 3, 6, 10, 18, 27, 54

(a) 10

(b) 27

(c) 3

(d) 6

(e) 18

Ques 3.

3 , 4 , 8 , 17 , 33 , 49 , 94

(a) 17

(b) 8

(c) 4

(d) 33

(e) 49

Ques 4.

36 , 49 , 100 , 144 , 196 , 256 , 324

(a) 256

(b) 36

(c) 49

(d) 144

(e) 100

Ques 5.

508 , 250 , 124 , 60 , 28 , 12 , 4

(a) 28

(b) 124

(c) 60

(d) 12

(e)250

Ques 6.

2 , 3 , 5 , 8 , 15 , 21 , 34 , 55

(a)5

(b) 8

(c)3

(d)21

(d)15

Ques 7.

2 , 5 , 10 , 18 , 26 , 37 , 50 

(a) 37

(b) 18

(c) 5

(d) 50

(e)2

Ques 8.

1 , 4 , 7 , 11 , 16 , 22 , 29

(a) 4

(b) 11

(c)22

(d)29

(e)1

Ques 9.

4 , 6 , 9, 18 , 34 , 59 , 95

(a) 34

(b) 6

(c) 18

(d) 95

(e)9

Ques 10.

54  , 43 , 34 , 26 , 22 , 19 , 18

(a) 26

(b) 18

(c) 43

(d) 22

(e) 34

solutions :

Ans 1. Each  term of the  series  is obtained by  multiplying the previous  term by 3 . 

⟹ Therefore the particular  order is  5, ( 5 x 3 = 15) , ( 15 x 3 = 45) , ( 45 x 3 = 135 ) , ( 135  x 3  = 405 )  , ( 405 x 3 = 1215 )., ( 1215 x 3 = 3645) , .. and so on . 

⟹ Hence , alternative  (e)  consists  of the wrong term.

Ans 2. In the  given sequence  second term is  1.5  the first , the third  term is 2 times  the second and so on,  Therefore , alternative  (a)  consists  of the wrong  term. 

 Ans 3. In the given sequence  difference between  successive  terms is in the order 12 , 22 , 32 .... . Therefore  58 should  replace 49  to from the series . 

⟹ Hence alternative (e)  consists  of the wrong term.

Ans 4. Terms  of the  series would be 62 , 82 , 102, 122, ...... 182 if 49  is replaced 64 . 

⟹ Therefore  , alternative  (c)  consists  of the wrong term.

Ans 5. If 250  is replaced by 252, then  difference  successive  terms of the series will  be in the order of 256 , 128, 64, 32 , 16 , 8  respectively which from a particular  order . 

⟹ Therefore , alternative (e)  consists  of the wrong term.

Ans 6.  If 15 is replaced  by 13 then a particular  order of terms in the series  will be formed in which  sum of two successive terms  is equal  to the next term.  

⟹ Therefore , alternative (e)  consists  of the wrong term.

Ans 7. If 18 is replaced  by 17  then terms of the series  will be  arranged  in the order of 12+ 1 , 22+ 1, 32 + 1 ....72+ 1 .

⟹ Therefore , alternative(b)  consists  of the wrong term.

Ans 8. If first term of the series is replaced by 2 then difference between successive terms of the series will be in the order of 2 , 3 ,4 ,5 ,6 ,7.

⟹ Therefore , alternative (e) consists of the wrong term.

Ans 9. If 6 is replaced  by 5 then difference  between  successive terms will be in  the order of 1, 4, 9, 16 ,25, 36 .

⟹ Therefore , alternative (b) contain the wrong term.

Ans 10. If  26 is replaced  by 27 , then  difference  between successive terms of the series  will be  on the  order of 11, 9, 7, 5, 3 ,1 .

⟹ Therefore , alternative (a)  consists  the wrong  term of the series.

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