Hello everyone! I’m a very beginner learner of Mandarin. I took the “measure words” class today and I was reviewing the lesson and I realized I have an unanswered question. I remember that the world “1” is Yi with tone 1, but for some counting words such as “wan” (碗) and “ping” (瓶) the tone of “1/yi” changes. (see picture below). Is there a rule about when the tone of the number before the counter changes?
Thanks in advance!