Double Digits: Mental Math

Answer two-digit multiplication in your head, instantly.
Interview math, exam questions, quick estimates at work. When two-digit multiplication gets fast, the time you spent calculating goes back into thinking.

Double Digits is a drill focused on one thing: solving two-digit multiplication again and again until it's fast. Use it to prepare for interviews and exams, or as a few minutes of daily brain training.

ACE THE NUMBERS IN INTERVIEWS
Consulting case interviews and trading firm mental math tests are done without a calculator. When two-digit multiplication comes instantly, you can keep your focus on the problem itself.

PREPARE FOR EXAMS
Many entrance exams don't allow calculators. Faster arithmetic leaves more time for the hard questions.

BE QUICK WITH NUMBERS AT WORK
"37 units at $48 each?" Answer on the spot in meetings and negotiations, and sanity-check estimates before you reach for a calculator.

A DAILY WORKOUT FOR YOUR BRAIN
Two-digit multiplication means holding numbers in your head while you calculate, which makes it an easy daily brain workout. Watch your times drop as you keep at it.

PRACTICE FROM JUST 10 PROBLEMS
In Practice, choose a number to learn and a range to multiply it by, and start with as few as 10 problems. It begins with 3 × 10–19. Go after your weak numbers and ranges as often as you like.

CONQUER EVERY NUMBER FROM 1 TO 99
In Challenge, take on 90 problems: your chosen number times every two-digit number from 10 to 99. Solve them all to clear it, and work toward clearing all 99.

SEE YOURSELF IMPROVE
Every finished run records your time and adds it to a line chart. A line sloping downward is your progress. The days you practice are recorded too, so you can keep your streak going.

COMPETE WITH OTHER PLAYERS
Challenge supports Game Center leaderboards, with a separate board for every number, so you can aim for the top on your best numbers. Signing in is optional; every feature works without it.

FEATURES
- A drill focused on two-digit multiplication
- Practice: start with just 10 problems
- Challenge: 90 problems for each number from 1 to 99
- Best times and progress charts for each number and range
- Daily streak tracking
- Game Center leaderboards
- Light and dark mode