# Aptitude - Odd Man Out and Series - Discussion

Discussion Forum : Odd Man Out and Series - Missing No. (Q.No. 8)
Directions to Solve
Insert the missing number.

8.
2, 6, 12, 20, 30, 42, 56, (....)
61
64
72
70
Explanation:

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.

Discussion:
12 comments Page 1 of 2.

Anirudh Rohith said:   5 years ago
2, 6, 12, 20, 30, 42, 56, (....)
6-2 = 4
12-6 = 6
20-12 = 8
30-20 = 10
42-30 = 12
56-42 = 14
72-56 = 16

We can get the answer in this way also.
(3)

Sushant said:   5 years ago
The sequence is (1 * 1 + 1),

(2 * 2 + 2) ,
(3 * 3 + 3) ,
(4 * 4 + 4) ,
(5 * 5 + 5) ,
(6 * 6 + 6) ,
(7 * 7 + 7) ,
(8 * 8 + 8) ,

And Now, the answer is 72.
(1)

Karthik said:   6 years ago
1^2 + 1 = 2,
2^2 + 2 = 6,
3^2 + 3 =12,
4^2 + 4 = 20,
5^2 + 5 = 30,
6^2 + 6 = 42,
7^2 + 7 = 56,
8^2 + 8 = 72.
(1)

Sourabh Singhal said:   6 years ago
2 * 1
2 * 3
2 * 6
2 * 10
2 * 15
2 * 21
2 * 28
2 * 36 = 72.

Pratik said:   7 years ago
The difference between successive numbers,
6-2=4.
12-6=6.
20-12=8.
30-20=10.
42-30=12.
56-42=14.
x-56=16.
so, x=72.

Hema said:   8 years ago
The sequence is (1 * 1 + 1),
(2 * 2 + 2),
(3 * 3 + 3),
(4 * 4 + 4),
(5 * 5 + 5),
(6 * 6 + 6),
(7 * 7 + 7),
(8 * 8 + 8),

Jay said:   8 years ago

2^2 - 2.
3^2 - 3.
4^2 - 4.
5^2 - 5, and so on...

Kartik said:   8 years ago
The another logic is 1^2 + 1, 2^2 + 2, 3^2 + 3, 4^2 + 4.

6-2 = 4.
12-6 = 6.
20-12 = 8.
30-20 = 10.
42-30 = 12.
56-42 = 14.
x-56 = 16.
x = 72.

Another way :

2/1*3 = 6.
6/2*4 = 12.
12/3*5 = 20.
20/4*6 = 30.
30/5*7 = 42.
42/6*8 = 56.
56/7*9 = 72.