Quantitative Aptitude - Arithmetic Ability Questions

Given are the two AP'S:

15,12,9.... in which a=15, d=-3.............(1) 

-15,-13,-11..... in which a'=-15 ,d'=2.....(2)

now using the nth term's formula,we get

a+(n-1)d = a'+(n-1)d'

substituting the value obtained in eq. 1 and 2,

15+(n-1) x (-3) = -15+(n-1) x 2

=> 15 - 3n + 3 = -15 + 2n - 2

=> 12 - 3n = -17 + 2n

=> 12+17 = 2n+3n

=> 29=5n

=> n= 29/5

Here in the given series, it follows a pattern that

77 + 2 = 79

79  - 3 = 76

76 + 5 = 81

81 -  7 = 74

74 + 11 = 85

Consecutive adding and subtracting of prime numbers.

So the wrong number in the given series is 75.

Given number series is 5  19  49  101  181  295 ?

Here the series follows pattern that

5   19   49   101   181   295  ?

  14   30   52    80     114   (difference)

      16  22   28     34 (difference)

         6     6     6  (Common difference)

Therefore, the missing number in the series is ? = 295 + 115 + 34 + 6 = 449.

The next number in the series is

143 143 136 110

      0    7      26 (Differences)

 $$\begin{gathered} 13 - 1 , 23 - 1, 33 - 1, 43 - 1,... \\ Now the next number is given by \\ 110 - (43 - 1) = 110 - 63 = 47. \end{gathered}$$

Here the given number series  3, 10.5, 36.75, 128.625, ? follows a pattern that

3

3 x 3.5 = 10.5

10.5 x 3.5 = 36.75

36.75 x 3.5 = 128.625

128.625 x 3.5 = 450.187

Hence the next number in the given number series is 450.187.

The given number series follows a pattern that,

56

56 + 8 = 64

64 - 16 = 48

48 + 32 = 80 (Not equal to 90)

80 - 64 = 16

16 + 128 = 144 

Hence, the odd number in the given number series is 90.