Student: 100 white and black tiles will be used to form a 20x20 square pattern. If there must be at least one black tile in every row and at least one white tile in every column, what is the maximum difference between the number of black and white tiles that can be used?
Options:
(A) 75
(B) 70
(C) 85
(D) 90
(E) 95.
Another student: Let's say, hmmm...
Answer = B
Please refer diagram below
90 - 20 = 70 Final answer: (B).