Answer:

Step-by-step explanation:
There are only 2 solutions for none of the rooks can capture any of the other rooks: only if they are laid out in either of the 2 diagonal of the chess board
The number of possible combination for the rock to laid out in 8x8 (64 slots) chess board
possible combination
So the probability is pretty thin

Answer:
45
Step-by-step explanation:
Let the unit place be ‘x'
Tenth place be y
The number is 10y+x
x+y = 9 (according to the condition) (1)
Digits are interchanged Unit place' y ‘& tenth place ‘ x'
New no is 10x +y
This is 9 more than the original number
10x+ y = 10y+x +9
10x-x+y-10y = 9
9x-9y= 9
x-y = 1 (dividing by 9) (2)
Adding the two equations
2x = 10
x= 5
Substituting the value of x in first equation
y = 4
The number is 45, the original number is 54 this is 9 more of the new number.
It's 100 because 1000/10 = 1000