What is problematic with naming 2/3 "two out of three"? Give two reasons

The name used for 2/3 can be two-thirds. Two out of three can be also used, but it can be problematic.

For example, when you say you got two out of three in a test, but the test was out of 50 marks.

Naming it two out of three is lengthy and can be misunderstood.

Two out of three means that there are three of something, such as "I have ate 2 out of the three cookies, where what the fractions really would mean, "I have ate two thirds of the single cookie.