Calculation Training: Ottugi

Calculation Training is a timed trainer for mental arithmetic and estimation. ARITHMETIC (all free) • Pick the digits and the operation, from 1-digit to 4-digit numbers • Exam Mode mixes addition, subtraction, multiplication, and division at random COMPARISON • No exact answers needed. Just decide which side is bigger, as fast as you can • 7 types: fractions, products, multiples, growth rates, decrease rates, sums, and multi-term sums • Unlimited generated problems, with a free sample of every type GRADES • Every session is graded from S to D by your seconds per question • Wrong answers add a time penalty, so guessing fast does not pay off PAST EXAM NUMBERS • Comparison items taken from real Korean civil-service data-interpretation exams Supports English and Korean, light and dark mode. Premium is an auto-renewing subscription that unlocks full Comparison and Past Exam training.