20 boxes

There are 20 boxes numbered 1-20 and 20 students with IDs 1-20. All the boxes are initially closed. The student whose ID is 1 then opens all the boxes. The second student then closes box number 2,4,6 ---- 20. The third student then opens Box 3, closes box 6 and so on. Likewise, all students perform an operation on only those boxes, the numbers of which are multiples of their IDs. If a box is opened, the student will close it and if it is closed, he/she will open it. After all 20 students perform their respective tasks, how many boxes will remain open?

×

Problem Loading...

Note Loading...

Set Loading...