Q. On a chess board, in how many different ways can 6 consecutive squares be chosen on the diagonals along a straight path ?
(a) 4
(b) 6
(c) 8
(d) 12
Correct Answer: (b) 6
Question from UPSC Prelims 2021 CSAT Paper
Explanation :
Chess Board Consecutive Squares
There are 2 diagonals with 8 squares each on the chess board, and we have to choose 6 consecutive squares.
We will assume a block of 6 consecutive squares as one. So we are left with 3 places on the chess board where it can be arranged by selecting any one of the places out of three i.e., 3C1 = 3.
Similarly, for the other diagonal too, we will get 3 different ways. So, in total, we have 6 different ways of choosing 6 consecutive squares.
Hence, option 2 is correct.