Find out the wrong number in the given sequence of numbers.

36, 54, 18, 27, 9, 18.5, 4.5

3, 7, 6, 5, 9, 3, 12, 1, 15, ... has two different series

1) 3, 6, 9, 12, 15.....

2) 7, 5, 3, 1, .....

-1 is the next number.

Total savings = 200 + 200 + 200 + 240 + 280 + ... to n months = 11040

= 120 + 80 + 160 + 40 + 200 + 240 + ....n terms
= 40 + 80 + 120 + 160 + 200 + 240 + ...n terms
= n/2[2a + (n-1)d] + 80 + 40 = 11040
= n/2[240 + (n-1)40] = 10920
= n[6+n-1] = 546
= n[n+5] = 546
n = 21

The given series of numbers follow the rule that,

2880/6 = 480
480/5   = 96
96/4     = 24
24/3     = 8
8/2       = 4
4/1       = 4

But 92 is not in the rule. It is the wrong number in the given series.

The given series follow the rule that :

Multiplying consecutive prime numbers
2,3,5,7,11,13,17,19....
2x3 = 6
3x5 = 15
5x7 = 35
7x11 = 77
11x13 = 143
13x17 = 221
So, the wrong term is 165.

All except Parrot are birds of prey.

In the given series numbers are arranged following the rule,

55,44, 33, 22, 11

 Therefore, the missing number is 27.

There are two series, beginning respectively with 3 and 7. In one 3 is added and in another 2 is subtracted.

The next number is 1 - 2 = -1.

The pattern is 1 x 2, 2 x 3, 3 x 4, 4 x 5, 5 x 6, 6 x 7, 7 x 8.

So, the next number is 8 x 9 = 72.