Que: What is the missing number,
1, 4, 9, ?, 25
A. 15 
B. 16 
C. 17 
D. 18

 Ans: B
1*1=1
2*2=4
3*3=9
4*4=16
5*5=25
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Que: What is the missing number
-2, 1, ?, 13, 22
A.4
B.6
C.8
D 10

 Ans: B
(1*1)-3 = -2
(2*2)-3 = 1
(3*3)-3 = 6
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Que: What is the missing number in this series?
1, 4, 10, 19, ?
A. 33 
B. 31 
C. 30 
D. 28 
E. 29

 Ans: B
This is bcz each number is the sum with 3, 6, 9, 12
so 10+9=19, and 19+12=31.