The given series consists of squares of consecutive prime numbers i.e., 22 , 32 , 52 ,.....................,112 , 132 , 172 , 192 So, missing term = 72 = 49
125.
Which term of the series 5,10, 20, 40,...................is 1280 ?
(A) 10th
(B) 9th
(C) 8th
(D) None of these
Solution:
Clearly, 5 × 2 = 10, 10 × 2 =20, 20 × 2 = 40,.............................So, the series is G.P. in which a = 5 and r = 2.Let 1280 be the nth term of the series.Then, 5 × 2n - 1= 1280 ⇔2n - 1= 256 = 28 ⇔ n - 1 = 8 ⇔ n = 9
126.
Find the missing term: 125, 80, 45, 20, ?
(A) 5
(B) 8
(C) 10
(D) 12
Solution:
The pattern is - 45, - 35, - 25,........ So, missing term = 20 - 15 = 5
The given sequence is a combination of two series:I. 45, 47, 49, 51, 53 andII. 54, ?, 56, 57Clearly, II. consists of consecutive natural numbers, starting from 54.so, missing term = 55.
128.
What will come at the place of question mark ? 2/3 , 4/7 , ? , 11/21 , 16/31
(A) 5/9
(B) 6/11
(C) 7/13
(D) 9/17
Solution:
The sequence in the numerators is + 2, + 3, + 4, + 5 and that in the denominators is + 4, + 6, + 8, + 10So, the numerator of the missing fraction should be (4 + 3)i.e., 7 and the denominator should be (7 + 6)i.e., 13. Thus, the missing term is 7/13 .
129.
44, 41, 38, 35, 32, 29, 26, ... choose which pair of numbers comes next?
(A) 24, 21
(B) 22, 19
(C) 23, 19
(D) 29, 32
Solution:
Answer & Solution Answer: Option E Solution: This is a simple subtraction series, in which 3 is subtracted from each number to arrive at the next.
130.
83, 73, 93, 63, __, 93, 43. What number should fill the blank?
(A) 33
(B) 53
(C) 73
(D) 93
Solution:
This is a simple subtraction series in which a random number, 93, is interpolated as every third number. In the subtraction series, 10 is subtracted from each number to arrive at the next.