rounding up to two decimal points

Question

I just have a question regarding my answers in my exam paper, my teacher said to give the answer to two decimal points, I got the correct answer (2.89) but I rounded it up to 2.90. Now my teacher did not give me the mark for this and I want to know its worth asking or his right?

this is computing an eigenvector by the way, does rounding it change it that much?

heres his solution...

Answer 1

If 2.89 is correct to two decimal points, 2.90 is correct only to one. OTOH if the answer was 2.898, then to two decimal points the correct answer would be 2.90.

Answer 2

This is about what counts as a decimal point or not. $2.89$ is clearly three significant figures, but to me that's two decimals (digits after the point). The only thing that will help you here is to actually discuss this with your teacher and find out how he / she defines it.

Also, if you were supposed to round $2.89$ to $2.9$, then I would consider $2.90$ as wrong, since that $0$ implies more acuracy than you have.