Practice Test: Wrong Number Series - CAT MCQ

Therefore, wrong no. is 33

The solution is :
9 * .5 + .5 = 5
5 * 1 + 1 = 6
6 * 1.5 + 1.5 = 10.5
10.5 * 2 + 2 = 23
23 * 2.5 + 2.5 = 60 ≠ 90
60 * 3 + 3 = 183
Therefore, wrong no. is 90

The solution is :
8/2 – 1 = 3
18/2 - 1 = 8
38/2 – 1 = 18
78/2 – 1 = 38
168/2 – 1 = 83 ≠ 78
318/2 -1 = 158  ≠ 168
Therefore, wrong no. is 168

The solution is:
3 * 2 + 2 = 8 
8 * 2 + 2 = 18
18 * 2 + 2 = 38
38 * 2 + 2 = 78 ≠ 80
78 * 2 + 2 = 158
158 * 2 + 2 = 318
Therefore, wrong no. is 80

(11)² – 1 = 120
(12)² – 1 = 143
(13)² – 1 = 168
(14)² – 1 = 195
(15)² – 1 = 224 ≠ 226
(16)² – 1 = 255

Therefore, wrong no. is 253

Therefore, it must be 42+14 = 56   i.e.
127 + 56 = 183
56 + 15 = 71  i.e. 183 + 71 = 254
Hence, wrong no. is 185

The solution is :
7 * 1 + 2 = 9 
9 * 2 + 3 = 21 
21 * 3 + 4 = 67
67 * 4 + 5 = 273  ≠  275
273 * 5 + 6 = 1371
1371 * 6 + 7 = 8233
Therefore, wrong no. is 275

The solution is :
3 * 2 = 6 
6 * 2.5 = 15
15 * 3 = 45
45 * 3.5 = 157.5 ≠ 157
157.5 * 4 = 630
630 * 4.5 = 2835
Therefore, wrong no. is 157

Because, difference of the difference is prime numbers in increasing order therefore, wrong no. is 131