Having learned abacus formulas, it's time to show off your skills in solving number problems. When you feel comfortable to work on 2-digit numbers, you should move on to 3-digit arithmetic. Let's firs start with three and six 3-Digit number questions." How to Abacus Exercise" has more exercise books waiting for you to practice: 2 digits 34, 2 digits 567, 2 digits 810, 3 digits 36 and 3 digits 810. Check them all out.