In area of circles ch. The answers at back is written in fractions. Now i am confused what to do. If in my exams i write answer in decimals then teachers answer might not match. Also i divide everything in the begining so the teacher will not even get a link of my answer . What to do?

Dear student
We advise you to do the solution correctly, do the calculations carefully and then at the end leave the answer as it came (unless mentioned in the question  to leave the answer in fractions or decimals). Small change in digits after decimal will not make your answer wrong.
Regards