Lambs drink water once every two days, calves drink water once every three days and bears drink water once every four days. On May 1st, they drank water together and asked for a long time before drinking water together.
To teach you how to solve the problem, first list the number of drinks they have, as follows:
Lamb: May 1st, May 3rd, May 5th, May 7th, May 9th, May 10th, and so on.
Calf: May 1 day, May 4, May 7, May 10, May 13, and so on.
Bear: May 1st, May 5th, May 10th,
Therefore, the correct answer is May 10.