If the setup is right but arithmetic errors keep happening, slow down the mechanical part slightly and create a repeatable checking habit. Rushing a correct equation into a wrong answer wastes the strongest part of your work.

Write numbers clearly, align units, and do a quick reasonableness check before presenting the result. Short daily drills can also reduce the basic calculation load.

Track the exact error type. Percentages, zeros, multiplication, and transcription errors often need different fixes. If useful, this guide on case interview mental math gives more detail.