Suppose I'm teaching out of a textbook and there's a question which has a fairly-clear intended answer, but is flawed in some other way. Do I point out the flaw to the students? If yes: how do I answer the question "what if this shows up in the exam" (the exam is not set or graded by me)?

Example:

Q: If the ratio of the sides of a triangle is 1:3:5 and its perimeter is 63cm, find the length of the longest side.

It's pretty clear the desired answer is 35cm. However, the sum of any two sides of a triangle must be larger than the third side, which is not the case here, and the triangle is impossible.

Suppose I'm teaching out of a textbook and there's a question which has a fairly-clear intended answer, but is flawed in some other way. Do I point out the flaw to the students? If yes: how do I answer the question "what if this shows up in the exam" (the exam is not set or graded by me)?

As a notional example:

Q: If the ratio of the sides of a triangle is 1:3:5 and its perimeter is 63cm, find the length of the longest side.

It's pretty clear the desired answer is 35cm. However, the sum of any two sides of a triangle must be larger than the third side, which is not the case here, and the triangle is impossible.