Question

3 x 5 5 9 8 15 13 find x answer​

Answer 1

4 comes in place of x in 3,x,5,5,9,8,15,13

Given:

Series 3,x,5,5,9,8,15,13

To Find:

What comes in place of x

Solution:

Understand the series:

Arrange in pairs

(3 , x) , ( 5 , 5) , ( 9 , 8) , ( 15 , 13)

Note the difference between numbers in pairs

3 - x  = ?

5 - 5 = 0

9 - 8  = 1

15 - 13 = 2

Notice that This difference is increasing by 1  

Hence 3 - x must be - 1

=> 3 - x = - 1

=> x = 4

Hence , 4 comes in place of x

Another way to understand the series

Break in two alternate series

3    5    9   15

  2    4     6

     2     2            

(2nd Difference is constant 2)

x        5       8      13

   1         3        5

      2           2

(Keeping 2nd Difference  constant 2)

Hence  x + 1 = 5  => x = 4

4 comes in place of x