Questions

Number of spectral lines from a state n to ground state is

                   n(n-1)/2 = 6

1 + 1 = 121 = 1x1 1+1 1x1

1 + 2 = 134 = 1x1 1+2 2x2

2 + 2 = 444 = 2x2 2+2 2x2

3 + 2 = 954 = 3x3 3+2 2x2

3 + 3 = ?   

Similarly, 3x3 3+3 3x3 = 969

A computer has a CPU which is called as Central Processing UNit or a Processor builton the mother board. It has many components like control unit and Arithmetic and logical unit. 

The Arithmetic and logical unit of the CPU performs the arithmetic operations or mathematical calculations.

From the hints,

Only two options for 1st and 2nd digits => 4,2 and 9,3 since it is single digits

Sum of second and third digit  = 10 

If 2 => 3rd digit = 8

If 3 => 3rd digit = 7

4th digit = 2nd digit + 1 => (2+1 =3) or (3+1 = 4)

Sum of all digits = 30

Let 5th digit be x

=> 1st possibility = 4 + 2 + 8 + 3 + x = 30 => x = 13 (Not possible since it has 2 digits)

=> 2nd possibility = 9 + 3 + 7 + 4 + x = 30 => x = 7

Therefore, the PIN is 93747