Question

Mary has 6262 square blue tiles and a number of square red tiles. All tiles are the same size. She makes a rectangle with red tiles inside and blue tiles on the perimeter. What is the largest number of red tiles she could have used?

Answer 1

The factors of 6262 are
1x6262
2x3131
31x202
62x101

The first two are out, since there's no room for the blue border and red interior.

So now, check the others and pick the one which allows for more red tiles.

29x200
60x99