11x13

A short problem, nine answers, one correct — 11x13 trains mental math with no clutter and no words in the problems. THE BASIC OPERATIONS ARE FREE. NOW AND FOREVER. Addition, subtraction, multiplication and division with level bands that grow with you: from small times tables over carrying to the 11–19 tables — the app's namesake — plus chained problems like 47 + 8 + 6 at high levels. WITH “EVERYTHING” YOU PRACTICE EVERY OPERATION. One single purchase unlocks everything permanently — try it free for 14 days: • Percentages: from 50% of round numbers to surcharge and discount • Roots: squares and cube roots • Powers: up to powers of two and ten • Derivatives and integrals: from monomials to binomials • Geometry: symbol equations (▲ + ▲ = 12), counting corners, matching shapes Your progress grows per operation, syncs via iCloud, with progress charts and a Game Center leaderboard. Now with a true iPad layout and hardware keyboard support (keys 1–9).