Getting a math answer wrong should NEVER result in full credit for that problem. It’s fine to give partial credit, but you shouldn’t be able to skate by with partial or wrong answers as long as you can explain how you derived those answers. It’s not fair to students who can explain their methodology AND derive correct answers.
When I was in college, some professors gave full credit and some didn’t. I had one who required all answers to be calculated to six decimals and if you were off by one decimal for any answer, you received a zero for that quiz.
That's not what I wrote in my comment. I wrote that the student should be corrected.
I wrote that it is just as important to understand why you are wrong as well as why you're correct. Math is one of the very few subjects where you can prove beyond a doubt what the correct conclusion is and why.