Some of Helen's plants need water every day, some need water every other day, and others need water every third day. If she waters them all today, how many days will it be before she waters them all again?

Answer 1

look at the pattern
1,2,3,4,5,6,7 each day
1,3,5,7,9,11 every second day
1,4,7,11,every third day.

So what is the answer to the question?

Answer 2

7 days