Number Series Questions

Let first no. be "k" and multiple be "l"...start value of y with 3
then,
[(k x y) + {l x (l-1)}]
Thus, we get

15 x 3 + 3 x 2 = 51
51 x 4 + 4 x 3 = 216
216 x 5 + 5 x 4 = 1100
1100 x 6 + 6 x 5 = 6630
6630 x 7 + 7 x 6 = 46452

Therefore, the missing number is 6630.

Here the letter series is alternative reverse order series. So we get P, N.

The given series is 6, 6, 12, 36, 144, 720, ?

6

6 x 1 = 6

6 x 2 = 12

12 x 3 = 36

36 x 4 = 144

144 x 5 = 720

720 x 6 = 4320

Hence, the next number in the given number series is 4320.

The given number series is 10, 6, 8, 15, ?

10

10 x 0.5 + 1 = 6

6 x 1 + 2 = 8

8 x 1.5 + 3 = 15

15 x 2 + 4 = 34

Hence, the next number in the given series is 34.

Here the number follows the given rule 

 $$\begin{gathered} 23-1, 33-1, 43-1, 53-1, ... \\ \end{gathered}$$

But 28 has been given in problem series.

so 28 is wrong number.

First difference is 6 and second is 12. But if we take third as 18, then fourth difference will be 24. Then 93 can not be the last term.

So we have to take the difference as 6, 12, 24 and 48. 

So Answer is 21+24 = 45 

The given series follows a pattern that,

19 x 19 x 19 = 6859

18 x 18 x 18 = 5832

17 x 17 x 17 = 4913

16 x 16 x 16 = 4096

15 x 15 x 15 = 3375

So, the missing number in the given series = 4913