1. The problem statement, all variables and given/known data There're 60 bulbs in a classroom with 60 students. Initially all of them were switched off.Now gradually the students enter roll number wise and toggle the switches that are multiples of each of their roll numbers. For example, when roll no. 1 enters, he switches on all the bulbs(as they were all switched off initially), and when roll2 enters the room, he toggles the switches that are the multiple of 2 i.e. 2,4,6,8,10....so on.At last when the teacher entered the class how many bulbs did she find switched on?? 2. The attempt at a solution I took the roll no. of the students as i. Then he toggles the switches of the multiple of i. I couldn't find a way to solve this equation. Can anyone help me??