ch-14 Number Series : Introduction & Formula


Directions for Q. No. 1 to 5 : Find out the missing numbers :

1. 2,  9,  28,  65

(a) 121     (b) 195     (c) 126     (d) 103     (e) 9

Solutoin :

Ans : (c)

Method used to from the series is

(1)3 + 1, (2)3 + 1, (3)3 + 1, (4)3 + 1,….

Therefore, the missing number is (5)3 + 1 = 126

2. 2, 6, 14, 26,…. , 62

(a) 52     (b) 54     (c) 44    (d) 42     (e) 50

Solution : 

Ans : (d)

2 (+4) 6 (+8) 14 (+12) 26 (+16) 42 (+20) 62

The difference of each successive number is increased by 4. Hence, number 42 will fillup the blank space.

3. 101, 100, ….., 87, 71, 46

(a) 92   (b) 88   (c) 89   (d) 96   (e) 99

Solution : 

Ans : (d)

Difference of each successive number is the square of a natural number.

101   100. 196.1 87. 71 46