What should come next in the following number series?

9 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 7 6 5 4 3 2 1

Given that Vishal is 24th from either end of the row i.e from two sides

  1 2 3 4 5 . . . . . .24 23 22 21 20 . . . . . 5 4 3 2 1 

  Here before Vishal there are 23 members and after Vishal there are 23 members

  = 23+1+23 --> 47 members in the row.

The 2nd, 5th and 8th digits of the number 31549786 are 1, 9 and 6 respectively.

The perfect square of a two - digit even number, formed using the digits 1, 9 and 6 is 196.

And,  14 x 14 = 196 

So, the required even number is 14. Clearly, its second digit is 4.

Hence, the answer is (b).

Given Number : 7346285

Ascending Number : 2345678

Answer is Two. Those digits are 3,4

Given Number :      2 5 6 7 3 9 4 8

Ascending order :  2 3 4 5 6 7 8 9

Specified letters are 6 and 4 respectively.

Hence, required sum = (4 + 6 = 10)

The given numbers are :

382  473  568  728  847  629

When changes are made as given in the question, numbers become as follows :

238  347  856  872  784  962

Again now, find out the difference between the numbers given in options as given below:

(1) 473 - 382  => 347 - 238 = 109

(2) 629 - 728  => 962 - 872 = 90

(3) 629 - 847  => 962 - 784 = 178

(4) 728 - 847  => 872 - 784 = 88

Here the given numbers are 

567  284  696  865  738

When 1 is added to the last digit of each of the above numbers, it becomes as follows :

568  285  697  866  739

After reversing the order of digits , we get

865  582  796  668  937

Now , when the numbers are arranged in ascending order their order becomes as follows:

582  668  796  865  937

Hence , the fourth number is 865 (a number formed by 567). Therefore option(1) is correct answer.

Second, fourth and the sixth digits of the number are 3, 1 and 6. Using these digits only once we can make 361, which is a perfect square number. Hence, our answer is 19 x 19 = 361