Sumbolt: Mental Math Trainer

Sumbolt is a quick mental math trainer. Short timed rounds of addition, subtraction, multiplication and division, a daily challenge, times tables up to 20 and 12 speed tricks — on your phone, offline, with no sign-up. RIGHT ANSWER? NEXT ONE, INSTANTLY Type the answer on a big keypad. The moment it is right, the next problem appears. No Enter key, no fade-in, no waiting. A wrong answer shakes and adds one second to your time, so you keep going. TODAY'S CHALLENGE The same 20 problems for everyone today, made fresh every day. One round takes about a minute. Your first time of the day is your score, and your streak grows day by day. PICK YOUR LEVEL — ANY LEVEL, ANY DAY • Easy: 7 + 8 • Medium: 47 + 38, 24 × 7 • Hard: 382 − 57, 68 × 12 • Expert: 4825 + 739, 47 × 63 Add negative numbers, choose 10, 20 or 50 problems, or turn the timer off for calm practice. Every mode and every level is open from day one. TIMES TABLES 2 TO 20 Pick the tables you want to drill. No 4 × 1 or 0 × 1 filler. A times-table map shows which facts you have mastered and which still need work. 12 MENTAL MATH TRICKS Make a ten, add 9 as 10 − 1, times 11 for two-digit numbers, times 25, squares ending in 5 and more. Each trick has three short steps, a one-line "why it works", and 10 practice problems. SEE YOURSELF GET FASTER • Best time for every mode and level • Daily challenge trend for the last 30 days • Training calendar and day streak • Missed problems listed after each round, with "retry only the missed ones" MADE TO STAY OUT OF YOUR WAY • No music — just a short tick for right and a thud for wrong, and you can turn those off • Phone keypad (1 2 3 on top) or calculator keypad (7 8 9 on top) • Works offline, no account, your records stay on your phone • Home screen widget: your streak and one tap into today's challenge • Light and dark theme Great for adults who want to stay sharp, students before an exam, and kids practicing arithmetic with a parent. A minute a day is enough. Sumbolt shows ads. Watch one short video in Settings to have full-screen ads off for 24 hours.