**Directions (1 – 5): What will come in place of question mark (?) in the following number series?**

**1. 281 218 163 116 ?**

a) 77

b) 78

c) 56

d) 52

e) 85

**2. 900 810 440 392 180 ?**

a) 48

b) 150

c) 90

d) 45

e) 78

**3. 57 73 91 111 ? 157.**

a) 143

b) 133

c) 123

d) 135

e) None of these

**4. 57 85 105 117 ?**

a) 121

b) 108

c) 138

d) 136

e) 135

**5. 39 48 53 54 51 ?**

a) 59

b) 44

c) 33

d) 46

e) 48

**Directions (6 – 10): In each of these questions a number series is given. In each series only one number is wrong. Find the wrong number.**

**6. 3 16 19 46 55 92 105**

a) 3

b) 19

c) 46

d) 92

e) 105

**7. 3 12 30 60 108 168 252**

a) 12

b) 30

c) 108

d) 168

e) 252

**8.1/3 1/2 3/5 2/3 6/7 6/8 8/9**

a) 1/3

b) 1/2

c) 3/5

d) 2/3

e) 6/7

**9. 10 21 36 56 78 105 136**

a) 10

b) 56

c) 78

d) 105

e) 136

**10. 100 80 64 51.2 40.5 32.768 26.2144 20.97152**

a) 40.5

b) 64

c) 32.768

d) 26.2144

e) 20.97152

**Solutions:**

**1.**The series is 17

^{2}– 8 , 15

^{2}– 7 , 13

^{2}– 6, 11

^{2}– 5 , 9

^{2}– 4 , 7

^{2}– 3 , ……..

**Answer is : a)**

2. The series
is 10

^{3}- 10^{2}= 900, 9^{3}+ 9^{2}= 810, 8^{3}– 8^{2}= 448 , 7^{3}+ 7^{2}= 392, 6^{3}– 6^{2}= 180, 5^{3}+ 5^{2}= 150
, ………..

**Answer is: b)**

**3.**The series is 7

^{2}+ 8 = 57, 8

^{2}+ 9 =73, 9

^{2}+10 = 91, 10

^{2}+ 11= 111, 11

^{2}+ 12 = 133, 12

^{2}+ 13= 157,

13

^{2}+ 14 = 183,..**Answer is: b)**

**4.**The series is 6 × 9.5 = 57, 10 × 8.5 = 85, 14 × 7.5 = 105, 18 × 6.5 =117, 22 × 5.5 = 121, 26 × .5 =

117,….

**Answer is: a)**

**5.**The series is 6 × 9 – 15 = 39, 8 × 8 – 16 = 48, 10 × 7 – 17 = 53, 12 × 6 – 18 = 54, 14 × 5 – 19 = 51,

16 × 4 – 20 = 44, 18 ×
3 -21 = 33,…….

**Answer is: b)**

**6.**The series is 1

^{2}+ 2

^{2}– 2, 2

^{2}+ 3

^{2}+ 3, 3

^{2}+ 4

^{2}– 4, 4

^{2}+ 5

^{2}+ 5, 5

^{2}+ 6

^{2}– 6, 6

^{2}+ 7

^{2}+ 7, 7

^{2}+ 8

^{2}- 8….

Hence there
should be 21 in place of 19.

**Answer is: b**

**7.**The series is (1×2×3)/2, (2×3×4)/2, (3×4×5)/2, (4×5×6)/2, (5×6×7)/2, (6×7×8)/2, (7×8×9)/2

= 3, 12, 30,
60, 105, 168, 252

Hence there
should be 105 in place on 108.

**Answer is: c)**

**8.**The series is (1

^{2}+ 1) / (2

^{2}+2) , (2

^{2}+ 2) / (3

^{2}+ 3) , (3

^{2}+ 3)/ (4

^{2}+ 4) , (4

^{2}+ 4) / (5

^{2}+ 5) , (5

^{2}+ 5) /

(6

^{2}+ 6), (6^{2}+6) / (7^{2}+7), (7^{2}+7) / (8^{2}+8)
= 2/6, 6/12,
12/20, 20/30, 30/42, 42/56, 56/72

= 1/3 , 1/2,
3/5, 2/3, 5/7, 6/8, 8/9

Hence there
should be 5/7 in place of 6/7.

**Answer is: e)**

**9.**The series is 2 × 3 + 2

^{2}, 3 × 4 + 3

^{2}, 4 × 5+ 4

^{2}, 5 × 6 +5

^{2}, 6 × 7 +6

^{2}, 7 × 8 + 7

^{2}, 8 × 9 + 8

^{2},…..

= 10, 21, 36,
55, 78, 105, 136

Hence there
should be 55 in place of 56.

**Answer is: b)**

**10.**The series is 100 × (80/100) = 80, 80 × (80/100) = 64, 64 × 80/100 = 51.2, 51.2 × 80/100 = 40.96, 40.96 ×80/100 = 32.768, 32.768 × 80/100 = 26.2144, 26.2144 × 80/100 = 20.97152

Hence there
should be 40.96 in place of 40.5

**Answer is: a)**