There are 30 doors marked with numbers 1 to 30

There are 30 doors marked with numbers 1 to 30. There are 30 individuals marked 1 to 30. An operation on a door is defined as changing the status of the door from open to closed or vice versa. All the doors are closed to start with. One at a time, one randomly chosen individual goes and operates the doors. The individual however operates only those doors which are a multiple of the number he/she is carrying. For example, the individual marked with number 5 operates the doors marked with 5, 10, 15, 20, 25, and 30. If every individual in the group gets one turn, then how many doors are open at the end?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #30670