a chessboard of size 10*10 using alternative black and white squares is displayed on a computer screen one can reverse the color in a selected rectangular subarray of the squares by pressing ctrl+R find the minimum number of times one needs to press ctrl+R to make all the square the same color,either all black or all white clue:how many times one must press ctrl+R to convert the chessboard into alternate black and white strips a)10 b)20 c)9 d)50

• n=10
  source: https://mvtrinh.wordpress.com/2014/03/10/chessboard/
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• answer d.50
  since 50 black squares r there.we need to press 50 Ctrl+r to change the chessboard into a white board
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• chessboard: If n is even total clicks =n/2 +n/2=n
  If n is odd total clicks =(n-1)/2 +(n-1)/2=n
  So ans:10
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• Ans ) d-50
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• It ll b 10 times...u can draw and analyze fa 2*2 grid and 3*3 ..
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• D....> 50.
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• its 10*10 so total no of box are 100 and black and whit are alternate so so they contribute 1/2 of total
  so 50 black and 50 white hence he have to press 50 time
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• I think its 20
  
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• For 2*2 total attempt 2
  For 3*3 total attempt 3
  .
  .
  For 8*8 total attempt 8
  Hence,
  For 10*10 total attempt 10
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