Quantitative Aptitude: Number Series Set 70

Directions: The following series are based on a specific pattern. One number in the series is wrong. Find that odd one out.

1. 20, 9, 6, 5, 8, 15
   15
   5
   8
   6
   9
   Option C
   Solution:
   20*1-11=9
   9*2-12=6
   6*3-13=5
   5*4-14=6 (8)
   6*5-15=15.
   
2. 12, 7, 11, 31, 142, 1145
   31
   11
   1145
   142
   7
   Option D
   Solution:
   12 * 0.5 + 1 ²= 7
   7 * 1 + 2² = 11
   11 * 2 + 3²= 31
   31 * 4 + 4²= 140 (142)
   140 * 8 + 5² = 1145.
   
3. 2, 6, 20, 46, 98, 182
   20
   46
   98
   182
   6
   Option A
   Solution:
   2+4*1=6
   6+ 4*3=18 (20)
   18+4*7=46
   46+4*13=98
   98+4*21=182.
   
4. 4. 6, 10, 18, 45, 138, 618
   618
   45
   138
   18
   10
   Option B
   Solution:
   6…………. 10…………. 18…………. 42 (45)…………. 138…………. 618
   ……… +4……… +8 ……… +24……… +96 ……… +480
   ……………… *2……… *3 ……… *4 ……… *5 .
   
5. 10, 14, 28, 32, 66, 68
   68
   32
   14
   66
   28
   Option D
   Solution:
   10+4 =14
   14*2=28
   28+4=32
   32*2=64(66)
   64+4=68.
   
6. 2, 12, 30, 68, 130, 222
   30
   130
   12
   68
   222
   Option C
   Solution:
   1³ + 1=2
   2³+2=10 (12)
   3³+3=30
   4³+4=68
   5³+5=130
   6³+6=222.
   
7. 6, 3.5, 4.25, 8.25, 18.5, 48.75
   4.25
   3.5
   18.5
   48.75
   8.25
   Option A
   Solution:
   6*0.5+0.5=3.5
   3.5*1+1=4.5 (4.25)
   4.5*1.5+1.5=8.25
   8.25*2+2=18.5
   18.5*2.5+2.5=48.75.
   
8. 5, 12, 21, 41, 87, 214
   12
   21
   87
   214
   41
   Option B
   Solution:
   5+7 = 12
   12+(7+3=10) =22 (21)
   22+(10+9=19) = 41
   41+(19+27=46) = 87
   87+(46+81=127) = 214.
   
9. 20, 6, 5.2, 5.92, 7.96, 10.776
   5.92
   7.96
   5.2
   10.776
   6
   Option C
   Solution:
   20*0.2 +2 = 5
   6*0.3+3 = 4.8 (5.2)
   4.8*0.4+4 = 5.92
   5.92*0.5+5 =7.96
   7.96*0.6+6 = 10.776.
   
10. 225, 104, 185, 140, 161, 152
    161
    185
    104
    140
    152
    Option D
    Solution:
    225-11²= 104
    104+9²= 185
    185-7²= 136 (140)
    136+5²= 161
    161-3²= 152.