Abacus

A simple App to practice addition and subtraction for kids.There are four levels of practice.In first level there is only two digits to add and total time for exam is 40 second.In second level there is only three digits to add and total time for exam is 60 second.In third level there is only four digits to add and total time for exam is 100 second.In fourth level there is only five digits to add and total time for exam is 120 second.