Anyone trying to get into MBB or other top tier consulting firms knows the importance of fast math and estimation. Most of the tricky calculations you run into will be fractions and percentages. This app is specifically designed for those case interview scenarios where you are required to estimate the answer within 5-10% at speed.

Practice the fractions you commonly run into as well as more difficult fractions, and set the percentage accuracy bounds that your answer should fall into.
Works with iPhone 8 and above.