@grass (美丽人生): Can I do this way?
1. If the total number is Na for apple, Np for pear, No for orange,
2. and let maxNa = floor((Na/100) * (1 + 1/49)), and minNa = ceil((Na/100) * (1 - 1/49));
(*** or use 1/50 instead of 1/49 for more general cases)
and in the same way, we can get maxNp, minNp; maxNo, minNo;
3. in every one of these 100 boxes, put apples, the number should be within
[minNa, maxNa];
put pears for number within [minNp, maxNp];
put oranges for number within [minNo, maxNo];
4. then we can guarantee the numbers of apple,orange, pear in ***ANY*** 51 boxes will be >= the numbers in other 49;
(Note, there are some other ways to do it, too)