Question 776026
For a shoe to be usable it has to be in pair - one left and one right.


300 are left and 300 are right shoes.


There are 3 sizes each size having 200 pieces. Let the size 8 contain only left and 9 contain only right shoes. Since the no. of left and right shoes are 300 each then the remaining size 10 must contain 100 left and 100 right shoes.


Thus, minimum no. of usable pairs of shoes is 100.